I just met one of my mother's ex-boyfriends and he's really attractive. Do you think it's okay if I sleep with him?
Why do you want to sleep with him?
I think he's really good-looking and it might be fun.
It's understandable to be attracted to someone, but it's a bad idea to start a relationship with your mom's ex boyfriend. Doing so will create a very awkward situation for all of you, and it might hurt the relationship between you and your mom.
But what if it's only a one time thing?
I think even if you don't want to have a relationship with you mom's ex-boyfriend, it would still be a bad idea to sleep with him. I think it could cause a lot of tension between you, and it would probably end badly.