A few hours later, Jeff was horny yet again. His cock started to get hard and he began rubbing it through his pants. He thought, rather than just jerk off, he could ask his sister to take care of it for him. He took his pants off and walked into his sister's room.
Natalie was on the phone with one of her friends, pacing around her room, when she saw Jeff enter with his cock at full mast. She pointed at her phone, giving Jeff a lustful smile.
'Pussy or ass is fine, Jeff,' she said, covering the mic on her smartphone. Jeff walked in front of her and stuck his cock into her pussy, both of them still standing. Natalie's voice wavered.
'Oh really?' She struggled to say with her brother's cock in her pussy. Jeff guided her to the bed and laid her down, beginning to fuck her pussy slowly. Natalie accidentally moaned into the phone.
'Sorry what? Yeah I'm fine,' she said to the person on the other end.
Jeff started to thrust faster and faster, making it harder and harder for his sister to talk on the phone. She started to make up excuses about why she had to hang up, saying she was going out with her family. She hung up the phone, and let out a loud moan.
'Harder!' She cried.
As Jeff fucked his sister, he remembered his mother's incredible body. She was 40 years old, but her body was still youthful, and enhanced by her two pregnancies. He started to imagine Natalie as a MILF like her mother, visualizing her tits growing even larger, and her body growing fatter in all the right places. Jeff thrusted his cock as deep as he could into Natalie's pussy, and came, filling her womb. Perfect excuse to make her a MILF, he thought.
'Can we do another round?' Jeff asked.
'Fine with me, stud,' Natalie said, smiling lustfully.
Jeff kissed his sister and went back to the Chronivac, ready to alter his sister's body. He went to Natalie's entry and selected the MILF template, getting rid of any mental changes, but making Natalie think her new MILF body is normal. He also made her lactate a lot, forcing her to milk her huge tits every day. He hit apply, watching the avatar on the screen expand in all directions.
Jeff went back to his sister's room. Natalie's body was even more beautiful before. She was fatter than before, weighing at least double her previous weight. Her breasts had expanded from a E-cup to at least an FF. Her thighs were even thicker than before, and her ass seemed to never end. She had the perfect amount of fat on her belly, giving her beautiful love-handles. She was also taller than him now, by at least a few inches. His cock hardened instantly at the sight of his sister in her new MILF body.
'Get over here already,' Natalie said. Jeff put his mouth on his sister's breasts, filling his mouth with milk. He inserted his cock into her pussy, thrusting while drinking his sister's breast milk. Natalie moaned loudly.
'Jeff, I love when you suck my tits,' she said, rubbing her other nipple, milk leaking out of it. 'It makes me feel like a mom.' Jeff got an idea.
'Can I call you mommy?' Jeff asked, removing his mouth from her nipple.
'Sure, sweetie,' Natalie answered, already into it, as Jeff continued to thrust into her wet pussy. He latched onto his sister's other breast, filling his mouth with milk once more. Natalie rubbed her clit as her brother's hard cock slid in and out of her pussy.
'Mommy, I'm cumming!' Jeff cried, reaching climax.
'Do it baby, cum in mommy's pussy!' Natalie responded, wrapping her legs around Jeff's waist. Jeff unleashed a fat load into his sister's womb. He lay down next to his sister, groping her tits.
'Your pussy feels so good, mommy,' Jeff said to his MILF sister. She was already getting horny again to the sound of her brother calling her 'mommy'. They lay together for a while in bliss, as milk leaked from Natalie's giant tits. There were now two MILFs in the family, a development which Jeff was sure no one would object to. Drinking his sister's breast milk made him incredibly horny, he hoped he could do it more often.