Can an outside party contest a Revocable Living Trust?

The outside party are my two uncles. They were left out of their parent's trust/will. They thought they were each getting a home. Instead, one home is going to a grandson and the other is going to a great-granddaughter. Initially when my grandparents created their trust in 1992, both of my uncles were getting a home. But then an amendment in 1994 removed one uncle and another in 2002 removed the other uncle as beneficiaries to these two homes. My grandfather ped away in '95 and my grandmother just ped away two weeks ago. Our family lawyer sent out a copy of the will to everybody. They are unhappy, but again, are not beneficiaries in the most recent trust/will from 2002. Do they have any right to contest or can they even contest?