NC'd for this as it's outing... I don't think IABU but interested to see what responses I'll get.
FIL is having a birthday meal soon and invited DH, DD (2yo) and I. Now I don't like FIL, he's recently left his wife of 10+ years (not DH's DM) after having an affair for over a year. He did the same to MIL when DH was just a child. Best thing about it is he tried to bring OW over to our house the day after he left his wife! Who we are quite close to as she is DH's best friend's mum (FIL married DH's best friend's mum).
He also completely ignored DD's birthday this year. Not so much as a card or a call to say happy birthday. He hasn't been to see us since he's left his wife all because we won't welcome OW with open arms. He's also been getting cross at the fact were still close to DH's step family. Like he expected us to cut ties because he left them.
I've told DH I don't mind if he goes as he loves his dad but DD and I won't be going. If he cba to be a decent grandpa then why should we make the effort? I have no interest in meeting OW and playing happy families, I just want to leave them to it.