Edit: I am located in England

Edit 2: thank you for all of your advice I have taken it on board and it has stopped me from making a huge mistake, I will speak to a solicitor and my grandad, he may change his will to include my uncle for 25% but that’s up to him, all of your advice has been very helpful, I won’t he giving him a penny now.

My grandad, who is still alive, has left me his entire house in his will. However, his eldest son, my uncle now wants a piece of the house, he has said that either my grandad change his will and include him in it or that we pay him 25% of the value of the house.

My grandad has decided he doesn’t want to include him in the will and but we’re going to give him 25% of the value of the house. The house has recently been valued and is worth £80,000. This means he gets £20,000. I’m wondering what is the best way to give him this money so he doesn’t challenge the will after my grandads death, should we have him sign some sort of contract? Also my grandad has said he wants to transfer the house into my name entirely so that my uncle can’t challenge the will after my grandads passing.

Your advice is much appreciated and valued.

Thank you.