As he drank the milk from his sister's left breast, Jeff could feel his body changing. Nevertheless, he was addicted to her milk, and resigned himself to whatever changes the milk may cause. Jeff rubbed his cock through his pants as his body transformed.
Suddenly, he felt an intense pressure in his chest as his shirt tented. He paused drinking his sister's milk to take off his top, revealing a small pair of breasts, which were slowly getting larger. He pressed his face into Natalie's breast again, wanting to change more.
Jeff's waist pulled inwards, and his hips widened, giving him a feminine figure. His breasts were about C-cups now, and his nipples hardened. Jeff looked over at his father, who had grown breasts as well. Except for his thick cock, he looked almost entirely like a teenage girl.
Meanwhile, as her brother and father drank her breast milk, Natalie started changing as well. Her hips narrowed, and her jaw became sharper, giving her a manly look. Her clitoris pushed out until it was around 6 inches long, and her pussy closed up, forming her ballsack; she had grown a thick cock. Her muscles grew until she resembled a bodybuilder, and her cock continued growing, reaching a massive 12 inches. Her legs and torso lengthened until she was 7 feet tall, as Jeff shrunk into a more feminine size.
Jeff's cock began to shrink, and he started to rub it again. His scrotum and testicles pulled inside him, forming a vagina opening, and his shaft shrunk to the size of a small button, forming his clit. Jeff's new pussy started to get wet, as he, now she, stuck a finger inside.
Natalie's tits continued to recede, until Jeff and her father were sucking on Natalie's hard pecs, no more milk coming out. Natalie, now a man, directed his new sister towards his cock.
'Feeding time, sis,' Natalie said, as Jeff hungrily pulled his cock into her mouth. Natalie still had the responsibility of feeding her family, but in a much different way now.
Jeff sucked his cock as if it was giving her life, fondling his balls as his father in his new female body waited impatiently for his breakfast. Natalie came, and Jeff swallowed it all, filling her belly with warm, delicious cum. Jeff looked down to see her belly bulging from all the cum her new brother produced. She wiped her mouth, stepping aside to allow her father to suck Natalie's cock too.
Jeff felt up Natalie's hard muscles, the sight of which made her incredibly horny. She rubbed her pussy as she watched her father suck Natalie's dick, desperate for him to cum in her mouth.