DH's parents are very odd in their favoritism. They will go to plays, concerts, sporting events for all the other grand children other then ours. Our DS asked them if they would come to something of his and they said "oh, we will just wait until you are in high school before we start coming to your sporting events"

yet they go to my 5 year old nephews stuff all the time, whatever. When DH's brother moved to our town, DD who was 7 at the time said "well, maybe Grandma and Grandpa will FINALLY come and visit us for a change". They were down 3 times in 3 months to visit DH's brother and go to their kids' things. They have visited us about 5 times in 15 years.
BUT, they always say they would rather have our kids over to their house then the other grandkids because our kids are better behaved and easier to watch

. I don't get that one.
My mom is a total case and a half when it comes to favoritism. She is constantly buying stuff for my brother/sisters and their kids and nothing for me or my kids. One year at Christmas my brother got a new tv and my sister got a new microwave because her other one didn't work. Well, they had just BOUGHT a new one. It was MY microwave that was on the fritz. We didn't get anything that year because we didn't need anything. OK, whatever. The kids will sometimes get a gift from her for Christmas, but it is usually one of those $5 blue box Target gift things which is fine except that she will spend several hundred dollars on gifts for the other families and DH and I never get anything because "we don't need anything". My sister's kids get 25 gifts EACH from their other grandma, they don't need anything either, ok, whatever. Then she wonders WHY we don't like to visit because other then the obvious favoritism with the gift thing she is constantly telling them that they should change this or do that, nothing is ever good enough for her.
My dad and step-mom favor our kids but probably because our kids don't expect it like my sisters kids do.