How old is your brother?....

If he in any way is sexual with you or abusive and your parents are obviously not doing anything, then I would shake the tree a little and call the police next time. If he does this with his own sister then what will he do with another woman.... He needs help with his issues and fast, because it seems he wil be a menace to society if he continues this way.
Wish I could help more, but huggs to you.