If there was a trust created years ago and the mother passed away, leaving the husband or stepfather, what are the son's options at this point?

There was a trust created years ago and the mother passed away, leaving the husband or stepfather. Now he's passed away, but apparently modified the trust leaving all possessions to a cousin of his. Cousin claims there were now a trust "A" and a trust "B." However, only a few modification pages were sent as proof and there is no attorney information listed anywhere. He was under the impression that there was only one trust leaving certain things to him.