My wife used to go visit our daughters at college a couple of times a month. It took me a while to discover what they got up to together. I didn't like them doing it on my dime, so I gave them the freedom to do what they liked in the future. A flash BTB story, no sex.
Mark had to go visit his step-daughter, Hannah, at college. He got a late start and had to stay over night, expecting to sleep on the couch. While lounging he has to adjust himself multiple times and Hannah wants to know why.
Sitting at the counter waiting for his order, the truck driver dreams about the cute waitress and wishes instead of a piece of toast he could have ordered a piece of ass. Illustrated.
A short story with no revenge or hatred of the other spouse. Just a quicky about two parents that saw the writing on the wall and thought of their kids rather than themselves...