Brother died.no children. Had 3 siblings. In Louisiana. Left a trust to a woman he had know for 3 years, not lived with. Also left power of atty to her and her daughter a few months before he died. Do the siblings have any right to any thing. Some of the stuff was family property?"

You appear to be describing a Will which he left, not a trust. Are you certain that he left belongings in a trust - or did he bequeath them by Will? It matters.

And, no, if he left a binding document the siblings are not entitled to anything. The fact that he had known "the woman" for 3 years and didn't live with her is immaterial. He could have left his estate to a complete stranger.

Same with the power of attorney.

Also the minute he died, the POWER of attorney ends, it is only for them to sign for him while he is alive.

But how was the trust set up, was it though a will.

But if he owned it, it was HIS< if it was family property, then family would have their names on the title or deed.

He can leave his property and belongings to anyone he wants,