"Mom, I'm back from school."

"Hi, honey. I'm in the kitchen."

13yo old Mark walked into the kitchen and saw his mother making dinner fully naked. Her belly was noticably bigger than when he left that morning.

"Holy shit, mom! Are you pregnant?"

"No, your sister bet me I couldn't fit her head inside my pussy. She lost, so I cut her head off."

"That's awesome! Can I fuck her while she's still inside you?"

"Go ahead. Just try not to snuff me before I finish cooking. You wouldn't want the rest of your sister to go to waste."