My grandmother willed me a house! After she died, her son came over and never left! Now, I want him gone so II can proceed with my life! How can I make this happen?

You evict him like any other tenant.

Most places you have him served with a written 30 day notice to vacate, Florida its 2 weeks, parts of California it might be 60 days.

But you have to follow the eviction process if you knew he was living there... if this is all recent and you just discovered he was squatting there... contact your local police dept and see if he can be charged with tresspass.

Wouldn't this be you brother or, at least, a cousin?

In any case. He has established residency, so he it treated as any tenant would be. Since you didn't tell us where you are we can't tell you the prevailing laws. But you have to give him legal notice to vacate, then follow-up that up, if he doesn't leave, with going to court for an eviction order.