"I'm never going to look right, I'm so damn flat!" And with a plop, my cousin Shelley deposited her enormous rump on the couch next to me. She had always been a bit on the chunky side, but instead of inheriting her mother's big bust, she had gone bottom heavy. Family reunions didn't happen often, and it had been several years since we had seen each other, but honestly she looked good. It was a big butt true, but it was shapely, and it sent a surprisingly stiff signal up my vein. I put an arm around her and commiserated, "Yeah Shell, you deserve to have jugs like Aunt Sara," I said jokingly, but she turned to me, and in all seriousness said "Fuck yeah I do."

I paused and decided this could at least be fun if not very fortunate for me. I was a chemistry major and I'm fairly certain Shelley had dropped out of high school her final year. "You know, I could help you. You're dissatisfied with your breast size," she interrupted "Lack of breast size," "ah yes, lack of size. That can be remedied with the right amino acids and proteins, you just need a formula customized for your needs." She looked unbelievably and raised her eyebrows, "You wanna frankenstein my chest? Mad scientist bullshit?"

I quickly got up and told her of my studies and that genome mapping can show why our bodies grow and change, and that with the proper additives we can stay young longer, gain height, lose weight, and most importantly, grow larger appendages, such as breasts or penises. At the word "penis" she looked at my groin and noticed a very large outline and her eyes widened. "Damn, you happy aren't you? You have yourself a bigger dick in chemistry class?" I nodded slowly, "And bigger balls. You wanna try? For boobs I mean, not balls." Hesitantly she nodded and I helped her up. Okay, I'll need a hair sample and some time alone, lemme just," and I quickly pulled a hair from her head.

Into the garage I went after grabbing a protein drink from the fridge. I drank about half of it, poured in a double shot of rum, mixed it with soda and then jerked off hard thinking of her big bubbly cellulite ass. I got some cum on the side of the bottle, but most of it got in. Pants up, shaken not stirred, into the kitchen, glass, ice, and voila. A cum cocktail, no pun intended. I went back downstairs and presented her with the concoction. "It's designed for your DNA to aid it in growing huge boobs. I got you Shell. I would recommend you drink one a day until you know how it will affect you." She guzzled the sugary mixture down and gave a loud burp. "Wow, that was actually tasty. How fast do you think it'll work?"

"I would guess 24 to 48 hours. Just text me when you notice anything. The secret ingredient is kinda special and effects vary." Before leaving, Shell backed me into the garage, "Hey, my chest is tingling," and she giggled. "Can I have another mix for the road?" And then I told her, "I can mix it up for you, but you gotta know. The secret ingredient is opposite sex DNA that is blood compatible. You need testosterone to get bigger boobs, not just estrogen. So I'm using my DNA to help." She paused and started feeling her nipples. "So it's jizz? Yours? I don't care, just keep the boob grower coming."

I agreed and pushed her out of the garage, remixing the same volumes for the same flavor. I went back inside and motioned for her to come quick, and we both ducked back into the garage. "Okay, it's almost ready." I pulled down my pants and let her see my meaty balls in all their glory. "Okay, gotta get the cum from there to here," pointing from balls to glass. "I've already done it once today, a little help?" As she slowly sank to her knees and began stroking me hesitantly, I smiled and looked down at the big ass squatting behind her. I bet I could fuck it like a pair of titties, but if I had been looking at her front, I would have understood why she moaned so abruptly. Her chest had swelled just the tiniest bit.

Thanks for reading guys. Bonus points for me being a white dude and cousin Shelley being a black or a latina girl. Anyways, even though I'm lying out my ass to get my dick inside my cousins ass, she's actually going to gain some boobage up top. It can just be heredity finally kicking in, or the cum cocktail, and you get to decide her size gains, but she's eventually going to be in thrall to my balls. I'll deny her access unless she does increasingly demeaning or debaucherous acts. And all because she thinks this is working. And maybe it is. But who cares? Other kinks include, titfucking, deepthroat (all in), thigh job, handjob, cock praise, submissive female, impreg, hotdogging, and cum addiction. Limits are beast and pee or poo. Please dm, I do not use the chat feature ever.