Oh jools, I feel for you. I totally get this.
I have decided that they are not my priority any more. My immediate family is and as Mono is my immediate family now then he takes priority. I have told my brother this and his girlfriend and they objected highly. I am sure my parents would too, but I see no other way. If they are choosing to judge and not accept my life and my families life then they will not be invited to be involved. If they want to accept then their involvement will be welcomed.
As for them running into Mono, that's their problem. They have to deal with that. I had two birthdays, well four actually as a result of people around me not being able to accept each other... it made me sad on one account but I chose to look at it as a positive... I got more attention
Sometimes Mono is hear when they come over, unannounced (!). He is always around us... that is what we want and what he wants. It's their problem how they are with that.... I have decided not to invite them to formal gatherings he is at, we do them separately. It works better like that. In time it has gotten easier and works better for all of us all around. I know they have huge expectations of what we do and how we do it and I am trying REALLY hard to not get stressed out about the fact that I disappoint them. It's their problem, I see that, it doesn't make it easy though.... I hate disappointing anyone, ESPECIALLY my parents.
good luck my friend. I can image it would be MUCH harder having Mono live with us. I enjoy escaping to my Other Home (OH), where there is none of the bullshit... I miss him when he isn't here too though