What is going on with my family?

My older sister and brother in law have taken on a matriarchal/patriarchal stance within the family. Our mother died years ago and our dad is 83. They plan and execute every holiday, my sister does not ask "do you want to do thanksgiving? or xmas?", it's always done at their place and I always feel like an invited guest, an obligation. When cousins come to visit during the summer, everyone always stays with sister and bil, never with me and I live 5 minutes away and have 3 open bedrooms, they cram into my sisters house and all crowd in and sleep on the floor if they have to. My sister and bil never come to my house to visit, they tell me "you never invite us" - I tell them they don't need an invitation. If I did not stop over there 3 times a week and call, I would never see my family. My sister and bil do not bother with my fiance or I, they make no plans to see us and when we try they are always too busy with their plans and friends. It's been almost 300 days since they were over for a social visit, they have seen their neighbors and friends for numerous dinner parties and outings though. Xmas eve I made a nice spread but they had plans with the neighbors. They said they would stop by before going out but then called at the last minute to say they couldn't make it. I offered to make a new year's day brunch but could never get a definite yes out of my sister. I really think that they think they are kings of the hill and the family and do not not want to be in charge or something - it's like we are underlings or something and it's driving me insane, I want to move away, I'm hurt and pissed off.