[Cherry Christmas]

What distance are we talking about? Maybe your Mum could offer an olive branch and have them around for tea one evening? She really needs to be the one to take the initiative I think, they will have the kids in common so hopefully that will neutralise sarky remarks between the adults, if it goes well she could maybe do that once a month and try to reconnect the bonds, you could set things in motion by telling them how much she is missing your Dad and would welcome some family company, maybe they think she is not interested? Then get her to issue the invite after that it's up to both sides to make it work