I refuse to have a relationship with my bio father's wife or other kids even if it hurts them

My bio father is a deadbeat who walked out on me and my mom when I was only a baby. His family and I didn't talk all that much either when I was growing up. Once a year his parents would call and once every few years I would get a random call from one or two of his siblings. When I was 12 they informed me he had married someone and started another family. Three years later they asked me to reach out and have a relationship with the kids and maybe their mom and I said no. A year after I found out he got married, his wife found out about me. She got my mom's info from bio father's parents and she tried to bring me into the fold but mom told her I wasn't interested. She got in touch with me a few times after that begging for a relationship but I refused to entertain it. She even told her kids about me and they wanted to see me so bad that I could hear them trying to talk to me when bio father's parents called a few years later. I had to hang up and I stopped accepting calls from my bio father's family. I got a couple of texts telling me how upset the kids and wife were to be rejected. I can't say I ever cared. I feel no sense of responsibility for my bio father's wife or kids and I don't feel like having a relationship with them. They could reach out when they're grown and my answer will stay the same.