How can I feel this way about "family?"

I am so glad the holidays are over and it will be monthes before we have to deal with certain people again. Its very hard to be civil to people when they are treating your children like second class citizens and making you feel like you aren't even wanted there. I so wish we didn'thave to do this on a yearly basis or biyearly basis. I know my hubby loves them but they irritate him just as much as they irritate me and thats not fair to him.
They are truly his family and my children's family I am only related by marriage but its continous that we always feel unwanted. Last night was really bad. We went and were in one room and everyone else was in another. The kids weren't allowed in certain rooms of the house but other people were. I don't think that these people realize what they do to my kids. Do they realize that at a band concert for my 6th grader they showed up and my 3rd grader asked me who they were there for because they NEVER make an appearance at things for my kids. Oddly she was right they were there for a niece/cousin. Do they not realize that my children notice that they don't remember to call them for their birthdays, they don't care about getting a gift but they would like a phone call here and there. Do they not know that my kids notice that they never come around to visit us even though there is less than 10 miles from our house to theirs, but yet they go visit the other kids over a half hour away. The kids notice this, it has been this way for years, and it shouldn't bother me anymore but it does. I feel like my kids aren't good enough for them, they don't even know my kids. That is there lose I guess and it will be their regrets one day. I wash my hands at the whole thing, I don't want "family" that doesn't want us. :(