I don't want to maintain a relationship with my birth family

I was curious how many adoptees really don't want to maintain a relationship with their birth families. I was adopted at age 2 nearly 50 years ago and I accidentally ran into my birth father at age 35. He began doing business at the company I work for and we look exactly alike. Coworkers started joking or even asking if he was my dad. We didn't just look alike a little, we were like twins so I knew there had to be more to it. When I told him I was adopted he told me that he had given up a child for adoption and voila, it turns out he was my biological father. I found out I was adopted at about age 12 when I needed to present my birth certificate at school for some reason. I looked at some of my friends' birth certificates and they all had the doctor's signature on it, but on mine the doctor's name was typed. When I asked my parents why, they nonchalantly said "oh, it's because you're adopted". I really don't know why I didn't ask or talk about it, maybe I thought they were joking at the time but I was not even curious about having been adopted. Then high school came, I was a super jock and really popular, parties and sports events, and homework took up a lot of my time so I didn't even think about being adopted or who my biological parents were. Later in life it seemed more of an issue for other family members, my cousins, my spouse, my children but although I had a bit of curiosity I didn't really care to look for my biological family. Then at age 35, about 15 yeas ago is when I started to meet my biological family. It seemed cool at first. After all, I looked exactly like my biological father. And perhaps he had money and could help me out a bit. But then things started to bother me, like when my biological dad would say, "these are your grandparents" and I thought, "no they're not". When he tried to tell me about his culture and ethnicity, I felt absolutely no connection. All of these cousins, aunts, uncles etc started appearing in my life and I really didn't want to have anything to do with them. It's not like I disliked them, but I felt no connection, like they were strangers and about 2-3 years after meeting my biological family, I was trying for figure out how to break of contact with them. I didn't want to be rude because they had done nothing wrong, but they were about as "family" to me as a coworker or person I see on the train every day. Luckily for me, things just kind of faded out anyway. I don't know if they got the message or if I sent some type of signals out, but the contact did stop. I do get a call once or twice a year from my biological dad, or, as I have begun to refer to him as "genetic dad" because all he basically gave to me was his genetic material. We are cordial and I am nice to him, although sometimes to be honest, I am just pretending. I don't consider him a part of my life, just a sort of acquaintance. I don't like my biological or adopted children referring to him as grandpa either. The funny thing is that my two adopted children feel the same way as I do. They have absolutely no desire to meet their biological families. In fact, I gave one of my adopted boys contact information and arranged a meeting between his bio family and him when he was in junior high and it never worked out. He never wanted any contact with them and to this day he throws it in my face and tells me I should have never encouraged him to meet them. I wonder if there's something in my attitude or personality that rubbed off on my kids as well. I wonder if there's just a certain personality type that could care less about the biological relatives. I see so many reunion stories on talk shows, in the paper, online and I just find them weird. I wonder what percent of adoptees could care less about meeting their biological families. To be honest, the only thing I wanted to know about my biological family is what they looked like and if they had any money. If anyone else feels this way, please share. Sometimes I really feel weird, perhaps cold for feeling this way. My spouse, after all of these years, finally seems to understand my feelings. But so many people are often puzzled by my attitude.