Quoting Stfu Shirley:" Your grandma's badass"
Op, if you think money is the reason they're getting in touch, then maybe your family feels like the grandpa owes you guys something ?
It makes me think of my brother. He disowned all of us when I was like 12. He got back in touch when my great grandma was on her death bed. (8 years later) I thought it was mainly because he figured she had a stash of money hidden.
What he failed to realize was that out of all of her great grandchildren, I was the favorite