NC'ed because I'm paranoid.
There's a long history with the IL's, but the essence is my SIL and BIL (DH's sister and her DH) like to come round a visit. Problem is that when they do come, they're often really grumpy and a bit aggressive. They won't smile, no manners, and are just generally low level unpleasant, or ungracious as my DH would say. This sets my anxiety off, so even if I know they're visiting MIL I will start worrying that they may drop by. There are exceptions when they're lovely. It's like a switch.
My SIL is very secretive and won't talk to me about anything. She will exclude me in family discussions about her elderly parents care, which is fine. I respect that. So I have no idea what's going on with her or what she might be dealing with, I just get the grumpiness. MIL will try to explain, but obvs she will also be respecting confidences.
My DH is great, and mostly he will go and see them at MIL's house, but she's elderly and I don't want him to feel like his family can't come round.
The question is: how do I handle this? It impacts on my family life because I get tense, the kids pick up on it, and generally the atmosphere is pretty awful. Christmas is looming. I feel like telling them to snap out of it or go somewhere else but that would cause WW3.
How would you handle it?