Well first of all, ya that is rough. Do you know what his sentence was?

I mean I think you should ask your mom about it. She definitely knows the story because she was with him at that time. Maybe it was a mistake kind of thing. Like with his alcoholism; went out; drank way too much; a woman came onto him. He blackout had sex with her. Maybe he didn't even remember it happening at all. Overall, misinterpreted the consent. She charges him with assault...

I don't know. I mean its a horrible crime. But maybe that's his only criminal offence. Like.. maybe he wasn't a serial rapist or anything you are possibly fearing.

Don't get me wrong. Sexual assault is very bad. I'm not denying that. But maybe you won't think of him as such a horrible person if you learn it was an honest mistake/mix up and he actually isn't a horrible person.

It would just suck to form a negative opinion of someone you loved... like your father after his death. I think you should ask.

Find out details before you share it with your sister (if you decide to)