No Connection to extended family.

I'm 29 and I was adopted at birth. Both my sister and I (she is younger, different birth mom, different city) are adopted. Our adopted parents, my Mom and Dad, have been amazing and I honestly can't imagine my life without their love and support. The four of us are really close, but to me, my love and connection to my extended family stops there. I've never really connected to people super easily. I'm an open book with a closed heart, if that makes sense. I feel absolutely no connection to my living grandma, to my aunt, uncle and cousins who I see a handful of times a year. I receive so much flack from extended family about not visiting/calling my Grandmother a lot. I honestly have no desire to. There has also been years of comments (on her end) to me about certain things that have always sat negatively with me, which doesn't really help this situation. I try to avoid family functions because I feel alone and disconnected. I never really felt/thought about this until recently when most of my friends began to get married and would see how close they were with their grandparents, cousins and extended families. This is extremely hard for me to talk to my parents about, specifically my Dad as it is his mother and his side of the family .... he would never understand where I'm coming from. Im just wondering if anyone else has struggled with the same sort of feelings?