Relationships with in laws are largely outside your control; you can manage your own side of the interactions but not theirs. I’ll be married 30 years this summer, and my spouse’s siblings have always been a thorn in my side, getting worse over time, not better. Small things can fester, particularly when you are dealing with grudge holders like I’m stuck with.
We manage things by minimizing contact. Sad that it has to be that way, but the alternatives are all worse.
Good luck. Don’t expect the in-laws to improve in any meaningful way.