I say this as your friend but be aware that some creeps on this site keep an eye out for posts like this to satisfy their disgusting fantasies.
Nonetheless, you deserve a place to talk about these things and people like myself will be here to hear you.
I'm sorry this happened. Someone your family trusts and someone you grew up with, doing a thing like that. They're so integrated in your daily dynamics that I'm sure it's indescribable to manage all by yourself. Your family should be there to support you and spot something like this but instead they do things like you mentioned on Christmas to make you even more uncomfortable.
It makes me angry just hearing about it. This is horrible. Hugs.