The Day My Sister Asked Me to Examine Her

Ever since I can remember, sex has fascinated me. That isn’t a confession meant to shock, nor a boastful remark: it’s simply the truth. In every situation, in every conversation, in every glance crossed on the street, my mind always ended up drifting toward the same place.

My name is Mateo, I’m twenty-four, and I’ve just finished medical school. I grew up in a house where the profession was almost a surname. My father, Esteban, has for years been one of the city’s leading trauma surgeons. My mother, Carolina, works as a plastic surgeon in a private clinic and is, without quite realizing it herself, the woman who has marked me most.

At forty-eight, she still has a figure that turns heads. I grew up watching her get ready for dinners, come out of the bathroom in her robe, pose with the easy confidence of someone who knows she’s attractive but doesn’t bother showing it off. She was my reference point from adolescence onward. She was also the reason for countless nights with the door locked, my hand around my cock, her image fixed in my head, imagining what it would be like to bury my face between those tits that showed in the neckline of every dinner dress.

There were four of us at home. Except for my sister Lucía, twenty years old, second-year psychology student, mirror girl. We called her by her full name because Mom is also called Carolina, and two “Caros” in the same house was too much. Lucía had the body of a woman who knows how men look at her in the street: a narrow waist, long legs, a round, firm ass that pulled any pair of pants tight, and a smile she practiced in the hallway mirror. The only thing that tormented her were her breasts. She said they were small. To me they looked perfect, but some women find a flaw in what others would call a miracle.

For months she had been asking Mom for an operation. She wanted it no matter what.

—Honey, wait until you’ve finished developing —my mother would repeat—. When you turn twenty-two we’ll talk about it seriously.

—But it’s already all done —Lucía would protest.

—Not quite. And I don’t want to retouch something that may still change on its own.

I, who enjoyed putting venom where nobody had called me, would add my part.

—Mom, when you operate on her I want to be in the OR with you. As a man, I can advise you better on size.

—Dream on, Mateo.

—I’m only helping. Professionally.

—Honey, don’t listen to your brother and his nonsense.

I knew perfectly well what I was planting with those comments. And I knew that, sooner or later, one of them would take root.

***

It took root on a Tuesday in June. My parents had gone out to dinner with colleagues from the hospital and the two of us had stayed home alone. I was in my room reviewing notes for the residency exam when I heard her voice from the other side of the hallway.

—Mateo! Got a minute?

I put down the book and went. Lucía was sitting on the edge of the bed, barefoot, wearing an old T-shirt and cotton shorts. She had that look of someone who’s been rehearsing a question for hours.

—You were serious? —she asked.

—About what?

—Helping me choose the size.

I pretended to think about the answer. I was thinking, just not about what she believed.

—Of course, little sister. You’re my weakness, you know that.

—And how do you figure out the ideal thickness?

—Very easily. But if you want, we’ll do it properly, professionally.

—Okay. What do I do?

—I need you to take your clothes off.

—Are you insane?

—Lucía, to take real measurements I need to see your whole body. That’s how they taught us in college. If it makes you uncomfortable, we’ll stop.

She looked at me for a few seconds. I could see the whole dilemma cross her face and then that expression that comes when someone decides to accept what they wanted from the start.

—Okay, anyway, we’re siblings. And you’re a doctor.

—I’ll treat you professionally —I promised.

I was lying, and we both knew it.

She started with the T-shirt, crossing her arms and pulling the fabric upward with that calculated slowness of someone who knows she’s being watched. She wasn’t wearing a bra underneath. Her tits were bare, white, firm, the pink nipples pointing upward, smaller than the areolas and already hardened by the room’s cool air. Then came the shorts, which she let fall to the floor by kicking them off with her feet. And, without looking at me, her panties too, a pair of white cotton briefs that slid down her thighs to her ankles. The wet stain in the center gleamed against the backlight, betraying her before she even opened her mouth. I was in pajamas, with no shirt and nothing on under the pants, and my cock, already rock hard, strained the fabric with an obscenity no crease could hide.

—You’re getting turned on —she said, amused and almost proud, eyes fixed on my bulge.

—Relax, I’ve got it under control. But what a body you have, Lucía.

She blushed, but the smile that followed was anything but innocent.

I started with her waist. I circled her skin with both hands and moved upward slowly, with almost no pressure, to the contour of her breasts. I cupped them with my palms and felt how hard her nipples had gotten before I even touched them. When I pinched them between my forefinger and thumb, a short moan escaped her, too late to swallow back. I leaned in, pretending to be the exacting doctor measuring, and breathed against her skin. I felt the hairs on her arms rise. I licked one, slowly, tracing a circle around the areola before sucking the whole nipple into my mouth. She arched her neck and buried her fingers in my hair.

—Fuck, Mateo…

—Still measuring —I whispered with her tit in my mouth.

I slid one hand down her stomach. She didn’t protest. I reached her hipbone and lingered there, measuring nothing, registering everything. My fingers slipped toward her pubis, barely covered by a trimmed, soft strip, and from there I went a little lower, brushing the top of her cunt with the pad of my middle finger. She was burning hot and soaked through. When I pulled my finger away it was gleaming, stringing a little bridge of wetness back to her.

—Your waist is what helps me calculate the proportions —I said, in a very serious voice, bringing the finger to my mouth and sucking it in front of her eyes.

She closed her eyes and nodded, biting her lip. I turned her body gently to have her back in front of me, put my hands on her ass and parted it with my fingers. Her ass was a spectacle: two firm half-moons opening to reveal the pink little asshole and, lower still, the swollen lips of a dripping cunt. When my hand slid between her legs and I cupped her sex, I heard the first stifled moan. I pushed a finger in without warning, all the way to the hilt. She folded forward, bracing herself against the wall.

—This counts for the size too —I murmured against her nape, moving the finger inside and adding a second—. You need to be well dilated for the proportions to work out.

—Mateo…

—Yes?

—Stop pretending. Fuck me already, goddamn it.

I opened her cunt lips slowly, parting them with two fingers while my thumb circled her swollen clit. I started moving them with my fingertips and felt her legs go weak and her breathing break into short gasps. I turned her, kissed her, and her tongue came into my mouth as if the search had lasted for years. And maybe it had. While we devoured each other’s mouths, she yanked the waistband of my pajama pants down and my cock sprang free, hard and slamming against her belly.

—Oh my God —she whispered as she looked at it—. It’s huge.

She grabbed it with both hands and started jerking me off, squeezing hard, sliding up and down with that greedy clumsiness of someone who can’t get enough of something new. She crouched without letting go, dropped to her knees, and took it all into her mouth in one shot. I felt it hit the back of her throat. She came back up, leaving a string of saliva hanging from the head, and went back down more slowly, sucking me with hollowed cheeks and eyes locked on mine. She sucked me like she’d been practicing for months, pulling back to lick my balls, taking them one by one between her lips, and then swallowing me again to the base.

—Fuck, Lucía, like that… like that, goddamn it, like a whore.

She took my cock out of her mouth only to laugh, her chin shining with saliva.

—Do you like it when your little sister sucks you off like this?

—I love it, don’t stop.

I shoved her onto the bed before I came too soon. I put her on her back, legs spread, and went straight to her sex. I parted her lips with my thumbs and drove my tongue from bottom to top, licking her with my tongue broad and flat from her asshole up to her clit. I licked her without mercy, my face soaked, closing my lips around her clit to suck it while I worked two fingers into her cunt and searched for that inner spot with a beckoning motion. She grabbed my hair with both hands and smashed my mouth against her sex, moving her hips against my face and biting the back of her free hand so she wouldn’t scream too loudly. When she came, she did it in less than a minute, her legs tensing and closing around my head, a hot stream sliding down my chin and a long whimper ending in laughter.

—If you don’t fuck me now, I’ll kill you —she panted, still trembling in the voice.

I did. I hooked her ankles with my elbows, folding her almost up to her ears, and fitted the head against her entrance. Slowly at first, watching her face, how her mouth opened when I went all the way in, how she arched her back and dug her nails into my arms. I slid it in centimeter by centimeter, pulling almost all the way out and sinking back in, so she’d feel it well. Her cunt was tight, burning hot, and it closed in rings around my cock whenever I brushed the bottom.

—You’re so tight, little sister.

—Rip me open, Mateo, don’t treat me like a little girl.

Then, without patience. I pounded into her with everything I had, bracing my hands on the mattress beside her shoulders, with those hard thrusts that made my balls slap against her ass and echoed all through the room. The bed creaked. She panted in my ear, biting my shoulder, asking me to shove it in harder. I turned her and got her on all fours, face smashed into the pillow and ass up, and drove into her again in one hard shove. I grabbed one cheek in each hand and spread them apart to see her better as I went in and out, her red, gleaming cunt wrapping around my cock, and the little asshole clenching with every thrust. I gave her a sharp slap on the right cheek and she moaned louder.

—Again, goddamn it —she begged.

I hit her again and left the red mark of my hand. I leaned over her back, grabbed her hair and pulled her head back, and bit her neck while I kept ramming into her. I slid a hand around to the front and rubbed her clit with my middle finger in time with the thrusts until I felt her tremble all over and cum a second time on my cock, soaking me to the balls. I held out a few more seconds, until my pelvis started trembling again. I pulled out just in time, turned her with a shove, and gave myself one last quick stroke over her tits, finishing in thick, hot spurts over her nipples, throat, and belly. She ran two fingers over her chest, picked up a drop, and put it in her mouth.

—Dummy, you could’ve finished inside.

—I didn’t know if you were on anything.

—I’ve been on the pill for three years.

I laughed. She did too. We lay there, sweaty, staring at the ceiling.

—Lucía…

—What?

—I know what size you need.

—Which one?

—I’ll have to examine you again to confirm it.

***

What neither of us knew was that my mother had come back earlier. Much earlier. A canceled appointment, a key turning in the lock without a sound, a scene she hadn’t expected to see and chose not to interrupt. She went back out and came back in making noise, as if she had just arrived. Lucía ran for the shower. I locked myself in my room, pretending to study.

The next day, while we were having breakfast, Mom dropped the sentence as casually as if she were commenting on the weather.

—Mateo, are you coming to the clinic tomorrow? My schedule’s packed and I could use a hand.

—Of course, Mom. I’d love to.

I suspected nothing. For me, going with her was a gift: learning from someone with fifteen years of operating-room experience was worth more than a semester of internships.

We arrived at the clinic around ten. The secretary, Sofía, handed her the day’s schedule.

—Ten patients, Doctor. Two waiting.

—Give me five minutes.

—Put on your coat —Mom told me—. And don’t speak unless I ask you to.

—Relax.

The cases went by. Reductions, augmentations, a nose job, the predictable stuff. The last appointment was different. In came a girl Lucía’s age, tall, light-eyed, with the messy beauty of someone who doesn’t need to try to have it.

—Come in, sit down —Mom said—. I’d like to introduce you to my son Mateo. He just finished his residency.

—Nice to meet you. I’m Renata, a friend of Lucía’s. I think we met at her birthday party last year, Doctor.

—Ah, of course —Mom lied with elegance—. How can I help you?

—I have the same complex Lucía has. She recommended I come.

—I’ll tell you the same thing I told her: you may still grow. I don’t like operating on breasts that haven’t finished defining themselves.

—I’ve heard that in other countries they ignore that rule. I thought maybe you could make an exception.

—Go behind the screen and take your clothes off. I’ll examine you and then we’ll talk.

Renata disappeared behind the curtain. I stayed seated, waiting for instructions that never came. Several minutes passed in absolute silence. When Mom called me over, her tone was strange.

—Mateo, come. Give me your opinion. You don’t mind, do you, Renata?

—Not at all, Doctor.

I crossed the curtain. Renata was completely naked, with no bra and no panties, sitting on the edge of the exam table with her knees slightly apart and her shaved cunt on display. She had no medical reason to be like that, and all three of us knew it. She held my gaze with a smile that was the first cousin of Lucía’s from the day before.

—Feel her —Mom said.

I touched her breasts with a calm I could barely maintain. They were a little larger than Lucía’s, with dark, broad nipples. I pinched one with a gesture that could pass for an examination and felt her breathing quicken and the nipple harden under my fingers until it was stone-hard. I slid my palm underneath, weighing them, and with my thumb I brushed the nipple again, rolling it slowly.

—They’re perfect —I said—. Just like Lucía’s.

—And how do you know what Lucía’s are like? —Mom asked, with a sweetness that fooled no one.

—Because she asked for my opinion too —I improvised.

Renata looked at me and smiled. The shameless girl was testing me. And my sister, obviously, had told her everything.

Mom ended the appointment with a date after summer. Renata said goodbye with two kisses. On the second one, she whispered in my ear, her hand brushing my bulge under the coat:

—You can give me that exam whenever you want too. And with your tongue, if you like, asshole.

She left the office leaving me with an erection impossible to hide under the coat.

***

—Close the door, Mateo. And tell Sofía she can leave now. We’re going to review the cases.

I did what she asked. When I came back, Mom had stood up and, before I could react, she grabbed me firmly by the crotch, squeezing my cock over my pants.

—So you like young girls, huh, you bastard? And your own sister besides?

—Mom, what are you doing?

—Don’t play dumb with me. When you went in, your mother had already come back. I heard you. I saw you. I saw you stuffing it into your sister like an animal, and I was touching myself against the door until I came.

She unfastened her coat, button by button, never taking her eyes off me. Underneath she wore a champagne-colored silk slip she always took off to keep her dress from wrinkling in the clinic. She let it fall to the floor. All that remained were thigh-high stockings and tiny black panties digging into her hips. The skin I saw then was not the skin of a forty-eight-year-old woman. The breasts, large, still firm, only slightly fallen, ended in dark, large nipples that had awakened from the moment I touched her. The flat stomach, with two dimples beside the pubis. It was the skin of someone who had gone too long without being looked at the way I was looking at her.

—Tell me, step by step, what you did with your sister.

—Mom…

—Start. And if you leave anything out, I’ll notice.

—Fine. Lucía, take your clothes off —I said, playing along.

She took off her panties without breaking eye contact, sliding them down her legs until they hung from one ankle. Her cunt was that of an adult woman, with slightly swollen lips and a thin, dark strip of hair over the pubis. It was already shining with wetness. And she challenged me with a silence worse than any order.

—Keep going. I want the full version.

I repeated every gesture I’d made with my sister. My hands on her waist, the pause at her breasts, taking them in both hands and squeezing until the nipples bulged between my fingers. I bent down and sucked one while with the other hand I worked the other nipple, twisting it, pulling gently. She let out a long gasp and grabbed my head against her chest. I lowered my mouth down her stomach, kneeling in front of her, and opened her cunt lips with my thumbs. I licked her clit with the tip of my tongue, slow circles, and then with my whole broad tongue from bottom to top.

—Mom —I said with my mouth pressed to her sex, breathing into her there—. Lucía was collateral damage. You’ve been my fantasy from the start. Every night since I was fifteen, with your picture in my hand.

She laughed. A broken laugh, amused, guiltless, while I buried my face deeper.

—You’re shameless. You’re sick. And I’m turned on by it.

—And you’re a liar. You knew exactly why you brought me here today.

She didn’t answer. She pushed me against the exam couch behind the screen, tore off my pants and pulled down my underwear, leaving my hard, tense cock pointing at her face. She stared at it for a moment, as if appraising a jewel.

—It’s just like your father’s —she murmured—. But thicker.

She knelt and took care of what she’d been waiting for all morning. She licked me first from the base to the tip, following the vein underneath with the tip of her tongue, and sucked my balls one by one, taking them whole into her mouth. Then she swallowed me. And by swallowed I mean it: she took me to the back of her throat, no gag reflex, and held it there for a few seconds with watery eyes and her mouth stretched wide open before slowly retreating. She repeated the motion again and again, spitting saliva over the glans and using it to jerk me while she sucked the tip. She looked up at me with those green eyes of hers, marking each thrust against her mouth. When I came in her mouth, with a brutal spasm that buckled my knees, she didn’t lose a single drop. She wiped the corner of her lips with her thumb, brought it to her tongue, and swallowed it.

—Delicious —she said—. Just as I imagined.

And before I could offer any apology, she already had me spread out over the couch with her body on top of mine, sitting on my face. She covered me with her thighs and crushed her cunt against my mouth without the slightest delicacy.

—Now it’s my turn. Eat me properly.

I ate her slowly, biting the insides of her thighs, playing with my tongue where I knew she could least endure it. I pushed my whole tongue inside her cunt, fucking her with it, and then went up to suck her clit between my lips like it was a candy, wrapping it, tugging it with gentle suction. I shoved two fingers in and found the inner spot at once, pressing with that beckoning motion while still sucking her clit. Her first orgasm came almost immediately, crushing my head with her thighs and shouting something that sounded like my name. I didn’t let her rest. I kept licking her with my face soaked in her release, harder, faster, until she came again, arching over me and grabbing the edge of the couch with both hands.

—Enough, enough —she panted, laughing—. I can’t anymore. Now fuck me, son. Fuck me like I saw you fuck your sister.

She stood up, turned around, and braced herself against the wall behind the screen, hands pressed there and ass toward me. I came up behind her, parted her cheeks with my hands, and ran the head of my cock over her dripping slit, searching for the entrance. When I found it, I drove into her all the way to the hilt. She screamed, a hoarse scream she swallowed by biting her forearm.

—Fuck, son, that’s how you fuck your mother.

I hammered her with everything I had, gripping her by the hips, watching her ass tremble with every blow. I leaned over her back to grab her tits from the front, squeezing them as I kept pounding her from behind. I bit her shoulder. She pushed her ass back, looking for me, syncing her hips to my thrusts.

—Harder —she begged—. Harder, goddamn it.

I pulled out, turned her, and put her back on the couch on her back. I spread her legs until they were almost straight toward the ceiling, resting her ankles on my shoulders, and drove into her again in that position that split her in two. I watched her face come apart with pleasure, mouth open, eyes closed, a thread of saliva escaping the corner of her lips. I pinched her nipples with my fingers while I kept pounding into her. Then I put her on top of me, lying back myself, and she took the reins. She straddled me, grabbed my cock with one hand, guided it in, and started riding me, looking down at me from a height that wasn’t only the body’s. She kept the rhythm with her hands on my chest, her tits bouncing toward me, her breathing heavy and rough. I rubbed her clit with my thumb while she went up and down. I felt her tighten around me inside and knew she was going again.

—Come with me, son. Come inside Mom.

—Can I?

—You can do anything. Menopause three years ago. Fill me completely.

We both came at once, without warning, biting our lips so we wouldn’t scream in a consultation room with thin walls. I felt her cunt clench in spasms around my cock while I emptied myself inside her in one stream after another, much more than I’d given her mouth. She collapsed onto my chest, sweaty, hair disheveled. When she got up, she stood with her legs slightly apart, and I saw a thick white line running down the inside of her thigh. She ran two fingers through it, collected it, and brought it to her tongue without taking her eyes off me.

—Nothing gets wasted in this office —she said.

***

That afternoon didn’t end with just once. Nor did what began there end that day. My mother and I became what neither of us would have admitted out loud: lovers. At home, when we could. But above all, in her Wednesday clinic, after Sofía left. My mother was far kinkier than I had suspected. She taught me to fuck her in the ass the third week, kneeling on the couch, with lubricant and patience, moaning like she had never moaned before. And I, apparently, was up to the task.

Lucía was not a one-off either. We took advantage of Saturdays, when Mom was on call and Dad played paddle tennis. My sister confessed to me, one of those Saturdays, with my cock still inside her and her ass seated on me, that with her previous boyfriends she had never felt what she felt with me. I didn’t know whether to flatter myself or worry.

Renata kept her word. She showed up one Saturday morning, supposedly to see Lucía, who had just gone down to the supermarket. She caught us mid-session, with Lucía on all fours on my bed and my cock going in and out of her cunt, and, without a second’s hesitation, she stripped right there and joined in. She sucked me off while I kept fucking my sister, and afterward the two of them took turns sucking me together, their tongues clashing over my glans while they groped each other’s tits. I came over both their faces at once, in spurts that fell over their lips and chins, and they passed the semen from one mouth to the other in a long kiss. Since then, Saturdays have become a routine that requires reservations, patience, and vitamin supplements.

The conclusion I’ve reached, after months of watching them, is simple. The innocence some men attribute to young girls isn’t really innocence at all. And their sexual maturity often arrives much earlier than ours. I thought I was taking advantage of a lapse. In reality, they’d been waiting for me to dare for a long time.