My daughter (6 yrs old) said that my nephew who is also 6, put his hands in her pants. We have the same drama. They have 4 boys they can't control, and then they get pissy when someone tries to discipline her kids.

But also she was sexually abused as a child, and might beat the crap out of him.
I don't want my brother to beat the crap out of the kid he is only 6. But I do not want it to happen again.

What do I do? To I call the school, and get advice from her teachers. I don't know. We always go over bad, and good touch, and that no matter what she can tell me anything. I just worry that if I make the wrong choice she will never tell me again.

What do I do?

Talk with your daughters counselor at school about the situation. Let her know that she can come to you or her counselor with any questions or concerns. Make your broth and sister aware. Tell them that you are looking out for your daughter. If they are offended, tough cookies, but they need to be aware. Hopefully they will get their son help. It sounds like he is curious and hasn't had anyone explain things to him... but just in case, make sure the two are never alone together. This doesn't mean cut them out of your life, just make sure the kids are always supervised when together. Explain this to your brother and sister as well.