There are several family members you can hook up with, and how to do so is different for each.
Brother
Slut route: Play soccer/football with him, watch porn, don't object to getting involved.
Other route: Don't lock the shower, let him look, invite him in to chat, let him shower with you, wash each other, get frisky.
Sister
Meet her boyfriend, talk to her about him, let them use the room for sex, spy on them, watch her sleep, touch her sleeping.
Stepdad
interact with him in the living room, don't lock the bathroom door, interact with him at his garage, eventually you can seduce him when he is in the living room or the garage as long as he is alone with you.
Real dad
Meet him at his work place, keep doing that.