A young high school senior was having a hard time getting a date for his prom. After almost giving up, his mom and dad suggested that he take his sister. The young lad didn't want to miss his prom so he agreed.

On the way home from the prom he took a look at his sister and said "If you weren't my sister I'd pull over and park". She replied "Pretend I'm not your sister".

So he pulled over to the side of the road.

This finally led to having sex together.

After they finished she said "Wow, your d**k is almost as big as dad's".

To which he replied "Yeah, that's what mom tells me".