What are the consequences of an amendment to a trust if it was never notarized?

My grandmother made two amendments to a trust. But it appears that neither were notarized. When the trust was created in 1992, each of her two sons were getting a home. But each of the two amendments removed them both and put on a grandson and a great-granddaughter as beneficiaries instead. In her last Will and Testament, she has the grandson and great-granddaughter getting a home. Which one is valid or which will hold up if contested?