i do have one sister who is 4yrs younger than me and I have talked to her about it. some of my dads behavior bothers her as well (inappropriate comments, walking through the house nude when we were growing up, etc)
she doesnt remember anything more than that but the time i think something would have happened or the feeling of a timeframe i get.....she would've been just a baby. i did once a few months ago ask my mom if there was a change anything ever happened to me when i was younger (just in genreal...not pinpointing my dad) and she was shocked i asked and more concerned if it meant H and I were getting divorced. sooooo im not really sure what other path to take aside from my dad himself or just doing nothing.