I like what everyone is saying on this thread, but Anvill’s posts really resonate.
The saying that we don’t have to go to every fight to which we are invited comes to mind.
Does this mean passivity and acceptance of ill treatment?
It does not.
Speak your truth if you would like to, PTF, as it sounds like it’s time and you are in a healthy place to do so.
Should you do this, you can probably expect pushback in the form of outrage, anger and doubling down of nasty behavior.
I think, ultimately you will want to remove this toxic person from your life, as best as you can.
I also think it will be messy as only family things can be.
Good luck and good thoughts.