So I’m living with my parents and they bought a house and added my grandparents name into the title…

So I’m living with my parents and they bought a house and added my grandparents name into the title deeds. It’s common to do that in our culture. My Parents paid for the whole deposit and finished the mortgage. Grandparents did not contribute a single penny. It’s a family home for everyone. The Purpose was for it to be my parents home. Now my grandfather has left my grandmother and married a younger model. 🙄🙄🙄His now trying to leave 1/4 of the house in his will for the younger model. We are soooo horrified and disgusted. Anyone have any advice on this ? We’ve looked into taking it to court but it’s so expensive!