My new girlfriend, Gina, is an insatiable sex-aholic.  We met at Tubbies bar, and she had my dick in her mouth within the hour.  She came back to my place, and we fucked and sucked all weekend long.  She moved in the following week, and we've been joined at the hips ever since.  After about a month of living together, she confided in me that she's bi-sexual.  I was cool with that, and occationally I'd come home from work and she'd have a women in our bed. Sometimes I'd join in, other times I'd just jerk off watching from my chair.  Some of her lovers were lesbians, some bi, like Gina.  Some even let me take pics or videos of them lezzing out.  The plan was, if she was bringing someone home, she'd text me and let me know. Thumbs up emoji meant I could join in, thumbs down  meant I would be a spectator with my dick in hand.  On this one particular day, last month, I got a thumbs up!

I silently entered my bedroom to a beautiful sight. My brunette goddess, Gina, laying in our bed, knees up, with a blonde girls' face buried in her muff.  Gina had the look of ecstasy on her face as she gave me the SHHH sign. I stripped naked and positioned myself behind the Stranger. She was ass up and face down on my girlfriend. Her ass was a perfect heart shaped invitation, so I dove in.  As my tounge first licked her folds, she pulled away. Then realizing what was happening, she pushed her wet snatch onto my face.   I kissed and licked her pussy, poking my nose in her tight bung hole.  As she got wetter and wetter, I licked all the way up and down, rimming her sphincter.  The Stranger was grinding her crotch against my mouth and tounge, moaning, as she continued lapping at Ginas' pussy.  I looked up at Gina over the Strangers firm ass, and her eyes were rolled back in her head.  Before I returned to the Strangers pussy, she groaned, "Fuck ME!" Gina opened her eyes and gave me the accepting wink.  I stroked my dick hard, and moved in behind the Stranger.  As I poked the head of my 8 inch tool into this new pussy, she gasped.  I slowly worked myself all the way inside one of the tightest holes I'd ever felt. As I began to fuck her, she pushed back onto my pole. I quickened my pace, my heavy balls slapping against her clit.  Each thrust of my cock would push her into Ginas' lap even deeper. The harder I fucked the Stranger, the closer Gina got to orgasm. We locked eyes, and I could tell she was close. Her hands were gripping the bedsheets, her thighs were tightening, and WHOOSH! Gina locked her thighs around the blondes head as waves of orgasms shot through her.  I wanted to make sure I didn't blow my wad too soon, so I stopped fucking the Stranger. Blondie started crawling up Ginas' body as my hard dick slipped out of her. She kissed Gina's belly, left nipple, right nipple, neck, and finally made her way up to kiss on her lips.  Gina was still quivering as they tangled tounges together.  The Stranger rolled over to give me the first look at her face.

"Emily?!"

 Oh shit! What was my baby sister doing here? Oh shit, I just fucked my little sister! Oh shit! I'm in so much trouble! Did she know it was me? Did Gina know she was my sister? Oh shit!

"Hi, Bro, that was amazing! I hope we're not done." Emily said.

My naked younger sister was cuddled up in my girlfriends busom, her blonde pubes on display, her ample breast staring at me as she started explaing how this happened. "I was at work tonight, bussing tables at Applebys, when Gina came in. She sat at one of my tables and ordered a drink. I told her I was too young to get the drink, but I'd tell her waitress.  Gina was the most beautiful women I'd ever seen, so I visited her table a lot.  We got to flirting and I thought maybe I was gay because I pictured myself with her.  When she was paying her tab with the waitress, I hurried to clear her table and get one last look. That's when Gina gave me a napkin with her number on it and told me to call her if I ever wanted to hang out.  I told her I'd be getting off in a half hour and would love to get her off after that!  I was shocked at my audacity!  Next thing you know, she drove me here.  I, of course, reconized your apartment, Bro, and my mind raced. Gina told me about your arrangement, and I thought, what the fuck!  I've looked up to you my whole life, Big Bro, so it'd be cool to get fucked by you and your girlfriend.  I never told Gina that I knew because I was afraid she wouldn't let this happen.   I'm so glad it did, though, aren't you?"

I was in shock! Emily was so "matter-a-fact" about the fact that we'd just fucked.  Gina looked baffled by everything that was happening. 

"Are you okay, Gina?" I asked.

"Actually, I think it's kinda hot!" she answered.

Gina and Emily got up on their knees and crawled towards me. Emily took hold of my dick and started stroking me. Gina started licking my ball sack, Emily stroking harder.  Then my baby sister put the tip of my dick in her mouth.  She sucked me for all she's worth while Gina had my balls in and out of her mouth.  For a fifeteen year old little sister, Emily could really suck a dick!  I was rock hard in minutes.  Both of my lovers turned around, offering me rear access to their beautiful pussies.  First I fucked Gina, then Emily. Back and forth, in and out.  The two of them were kissing each other while I switched off fucking them.  Emily could really twerk on my rod, while Gina used her muscles to squeeze and release my manhood.  I was getting close to cumming, and announced it to the girls.  They gathered under my cock awaiting their gift.  I first shot my load in Gina's mouth. She loves cum! Then I aimed the next at my Baby Sister. She took it like a pro. The two sucked me dry and kissed each other tasting my seed on their breathe.

After that, Emily was a regular in our bed.  Gina never got jealous when I'd ask her to invite my sister over. She had turned into a wonder lesbian lover as well as a sibling lover!  I loved the taste of my sisters' pussy juice on my girlfriends tounge. And Emily loved the taste of Ginas' pussy on my dick!  After about six months of this, and the one year anniversary of living with Gina, we decided it was time to introduce her to our parents.  I brought her over for Thanksgiving. That was one of the most erotic days of my life. But that's a story for another day.