My in-laws passed away fairly early in my marriage. So I had to deal with a sister-in-law. So to represent her side of the family, my husband and I would attend every freakin birthday party her kids had. Then when we started our family, they would make up excuses not to come. They preferred to spend the time schmoozing her rich aunt and uncle. Sometimes they would stop by for 15 minutes on the way home. My sister-in-law, her aunt and her aunt's daughter-in-law would go out to lunch together and even when I was unemployed would not ask me to join them.
Years later, all of us had moved to Florida and my sister-in-law divorced and re-married. She and her new husband called to say they were in the area and wanted to visit, ON ONE HOUR'S NOTICE. They arrived and stayed 15 minutes. During that time, her new husband kept talking about nicer houses that he had seen.
I used to feel bad about the fact that we were so low on their list of priorities. But as the years went by, these feelings started to fade. I don't expect anything out of them and I am never disappointed. I try to enjoy my life as much as I can. "Living well is the best revenge".