If somebody is abusing you sexually, that means they are doing the crime. And all we know, who does this kind of are worst criminal of this planet. You must go to authorities to solve this kind of issue. It does not matter who the hell they are.
If the person is your closest relatives. In that case, you should shout out to other relatives as well as authorities to unmask them. Don't worry about your reputation and how the society and your family going to say about you. Just take the action.
My friend, be the hero of your own story. Do not forget this kind of physical harassment, you should take strong action to diminish them.