If POA claimed to be the daughter of my grandfather took all of his insurance money, would this be something to look further into?

Lady claims to be my grandfather child, he was in a relationship with her mother before he had his biological children. My grandfather made her POA and she took all of his life insurance! He has four children and none of their names were on the death certificate but her name was on the DC. They received nothing, I believe she shouldnt have gotten away with that!