Your difficult relatives are fortunate indeed to have such a compassionate and caring person in their family circle. You are certainly not alone in having aging or needy relatives who are less than wonderful. But knowing that isn’t very helpful, is it?
I wish I had an easy answer to your question but I don’t. I do have some opinions but please do take into consideration that I only have a brief letter to go on.
I worry about the present emphasis I see everywhere about the importance of “boundaries.” Too often, it implies putting up a wall. I think it’s more useful to define it as putting up a shield. Walls keep people out. Shields deflect the barbs of words and opinions so a relationship doesn’t hurt us.
I therefore don’t agree that it is ever helpful to get “hard.” I do think you need to find ways to let the behaviors of the difficult people and the words and opinions of others roll off you.
There is an old saying: “Consider the source.” You don’t have to take in what these difficult people or uninformed people say. You don’t have to argue. You don’t have to justify, apologize or explain anything. Ideally, you will find a way to smile and nod and say innocuous things like “I’ll think about that” or “Thanks for sharing” and move on.
Then — and this is the important part — go to people who know the situation and who care about you for the hugs, validation, and support you deserve. You are blessed to have a stable and happy family. Don’t let the occasional visit with challenging people overshadow that.
Compassion isn’t something that people have to deserve. We do what we can to ease the lives of elderly and/or difficult people because it is the right thing to do. But it is equally important to do right by yourself by turning to your own network for support so you can keep it in perspective.
I wish you well.