I think you just have to sometimes (but not always) do things you dislike. I don't like some of DH's relatives, but it is reasonable to expect to have holiday meals with them. If I failed to do this, it would cause a rift either between us or between his siblings. Whether or not I like them, they are his siblings and I don't feel entitled to harm his relationship with them. He knows his sister is a sanctimonious, malicious gossip and chooses to accept her anyway. Since my family is deceased, yes, they would expect an explanation as to why he wasn't available on certain occasions.