How can I get the state to believe that my siblings were abused?

It isn’t being done to me. It is being done to my brothers and sister. ..My mother does indeed know about this. But the thing is is that we (me and my siblings) share the same father and not the same mother. Their mother and our father are fighting over who is the better parent. When the kids were staying with their mother. She had a boyfriend who was not very nice. As said above. One of your grandmothers took pictures of one of my brothers with the bruises. But the court will not believe it for the time being. And we don’t now how to get them to believe. As I said above I have always been there for them. Our step sister used to throw toys at them and they came to me cry. They knew I would help them and I did. But for the time I wsn’t there..all of this happend and now the kids won’t tell us because they think we will hate them. They don’t know that we know but it is very diffecult to know what happened. They go between Redding and New Mexico and I live far way from both places. Now not only do I feel that it is my fault but now I know why my siblings are the way they are.