Very sorry to hear that you're stuck with this situation. Common tactic for a mother to try and play off children against each other. Unfortunately, mothers seem to be masters at this behaviour!

It's uncomfortable and demeaning when we get blamed for all sorts of things, including others actions, when we've made the effort to bring them together. Have a longstanding issue in my family, with brother favouring company of his in-laws. Things he's said to me over the past years, that if I told my mother, think it would seriously damage her fragile health. He's always been the favourite, comes out with platitudes to her, to give him more time to do what he wants. Oh, and I should be grateful to him and his wife for inviting me there at holiday times. So that's another excuse for his poor behaviour.

In families, it's difficult to take sides. You must stay true to yourself. Sometimes it's impossible to heal a rift, the only person who'll suffer is you. Sorry to be so harsh!