As Phoster comments, there are statute of limitations considerations that vary from state to state. But even more decisively, I think the fact that your husband's brothers were minors would make it impossible to prosecute them.
If this is something your husband is thinking about, he should ask himself how doing this would promote his recovery. It would provoke a storm of emotions and turmoil and could traumatize him badly.
Nobody living can ever stop me
As I go walking my freedom highway.
Nobody living can make me turn back:
This land was made for you and me. (Woody Guthrie)