Ricky and Lisa have had a good life together, he is 11 years older than his little sister, practically baby sister for how big age gap was and maturity levels. He has seen her grow up from when she was just a baby, he even changed her diapers, bathed her in bathtub even up to age of 10, she always insisted but he finally cut her off. Ricky would also read her books, take care of any bullies or mean teasing, went to mall with her, pick her up from school, cuddle on couch together with her head resting on his chest and often fall asleep on him. With many other things he did with her, brotherly things and more times parental things more often that actual parents did; one day their parents died in a car crash leaving Lisa under Ricky's custody and now live with him permanently under his household, and receive an orphan's support check for each month for two thousand dollars.
Also recently when she starting going into puberty, Lisa had developed a never heard of condition; where her breasts have begun producing mass amounts of breast milk without being pregnant. Her breasts turned heavy and overburdened to point of causing pain and aching in her breasts so much that she has to frequently have her breasts milked or breastfed from for long period of time. Many times milk will dribble from her very erect and puffy nipples and soak her shirts. Ricky doesn't know yet about it, he just figured the wet spots was just sweat from the intense heat.
On a Friday afternoon during summer break for Lisa, and it being 100 degrees every day of the week outside. Ricky walks from his room to the living room to check on his little sister, he passes the couch and looks to his right seeing her bare ass completely exposed from her summer dress riding up. Lisa went commando underneath assuming from the stupid intense hot summer. Ricky saw perfect sight of her asshole and pussy lips with her ass propped up into the air, she was in perfect position to be taken from behind. He couldn't resist her beautiful ripe raw virgin body, while she was dead focused on her tablet doing something. He decides to test her, he grasps her ass cheeks and softly massages them, and running his thumb up and down along her ass crack. "What cha doin' on the tablet, lil sis?" He said casually, then leans over to look over and squeezes her ass cheeks tightly as trying to look.