DN (DP's sister's son) is being christened in two weeks' time an hour and a half away. MIL told DP that we will not be getting an official invitation as SIL is too busy, but has given us the time and location, and told us we are expected to attend. The date has been chosen to coincide with a family occasion in SIL's husbands family. DP feels duty bound to go with DS and DD. I admit that I can think of better ways to spend a Saturday, but AIBU to think that if SIL is too busy to invite us, it's not unreasonable not to go? SIL has form for treating family as a right rather than a privilege; I may be prejudiced against her.