She has the matching parts

Despite her warning not to, you look at your mother's waist. She seems to have both parts as well. Above her vagina is a beautiful, if soft dick. You run your tongue over your teeth thinking that if that thing got hard it could give you a real ride.

"What is going on?" she asks. "Why do I have a dick and my vagina?"

"Something strange is going on," you say, pulling down your own pants to reveal your matching set.

Your mom looks at you for a minute, and then back down at her own parts. They look identical. Exact matches.

"Shit, I have my own son's dick and he has the womb he came out of."

She sits on the bed.

"What are we going to do? How are we going to be normal?"

"I don't know mom," you say. "Maybe this is a sign. Maybe we should enjoy this." You sit down next to her. You grab her hand and have it wrap around your cock. You do the same. Your mother squeaks with excitement for a moment, and so do you.

"Maybe we need to fuck. It's like masturbation anyways, since we're just messing with our own parts."