Matt's breeding slut on his sister's head.

Matt held his sister’s head still as he finished writing and he smiled watching the ink vanish. He let go of her head and she went back to sucking his dick. After about a minute his sister stopped and stood up and started to strip. Matt decided to play ignorant as he asked. “What are you doing?”

“I’m getting naked so you can fuck me.” Lisa said as if it was the most natural thing in the world.

Matt pretended to be shocked and said. “But you’re my sister.”

Lisa finished stripping the last of her clothes and said. “Not anymore, I’m you’re breeding slut from now on. Now stick that dick in me and fill me with your cum.” She bent over and looked back at him waiting for him to do what she wanted.

Smiling Matt looked at his pen and said. “Just a second.” Grabbing her ass, he wrote all her pregnancies have zero genetic defects, if not pregnant is one hundred percent fertile, and orgasms every time her brother’s sperm enters her womb on her skin. Finished Matt slowly pushed his dick inside her as she gave a low moan in pleasure.

Lisa felt her womb grow hot as the pen changed her body. Looking at her brother she could not wait to start giving him children. Soon she was loudly moaning as her brother thrust his dick into her setting a good rhythm. A small voice inside her was trying to tell her this was wrong but that just made her get off more on the taboo of it.

Matt could feel he wasn’t going to last long after his sister had worked him up so well with her oral skills earlier. He started to thrust faster and deeper as his balls started to tighten. Slapping his sister’s ass Matt felt her pussy clamp sending him over the edge. Burying himself all the way inside her he climaxed painting her insides with his sperm. His sister screamed having her own orgasm as she thrashed wildly.

When Matt finished, he pulled out and watched his sister orgasm for the next thirty minutes. After she was finally done, she looked at him with naked lust and said. “That was amazing. If that’s how it’s going to be every time we fuck I’m never going to stop.” Matt got up and headed to his room his sister following behind him.