I just don't understand

Ahhh, family. So wonderful and yet so irritating at the same time. I am trying not to be completely and totally pizzed off at hubby's brother (W) and sis-in-law (L), but it requires a lot of energy. First, they get into a huge argument with their folks which happened while my father-in-law, who crawls in attics for a living, was helping out late in the evening with an electrical problem at their house. They don't speak for weeks, they ignore father-in-law's birthday and send flowers but don't call for mother-in-law's birthday. I try to overcompensate to make sure they know they are loved.

Then, they are a no show at Bubby's birthday party. No phone call, nothing. Weeks later they show up unannounced to drop off a present for him and also to invite us to my niece's party the next evening. Timing is suspicious.

We attend niece's party and bring invite to Smoochie's party. They happily accept and say they will be there. Halfway through Smoochie's party, L shows up with only one of their three kids. It was a lunch time party at a pizza place and L says they were late because they went to lunch first. Huh?

Smoochie has been begging to see the cousin closest in age (Flower). Flower is one year older. Hubby calls W several times last week. W finally answers phone last night. W insists we not only pick up Flower, but also her younger brother, Fish, because he gets his feelings hurt if Flower goes anywhere without him. Fish is three.

Hubby tells me over and over not to let any of this get to me. Please send zen thoughts my way because this might be a greater task than my capabilities.