I feel bad because I don't have a general love for my mother. Is this normal?

I am a 35 year old woman and I always knew my mother never liked my birth father. I have never seen nor spoken to him either. She gave me the impression he just ran off. Come to find out about three years ago I found out from my grandmother that my birth father actually d my mother when she was just 18 years old and that’s how I was born. I got a better understanding why she didn't really love me growing up. She never hugged or kissed me growing up and I have never heard her say she loved me. She never did anything special with me either except PTA meetings once in awhile. She says her mother never did that to her as well but my grandmother tells me she loves me and hugs me all the time. As an adult my mother and I have an ok relationship when shes not going thru something, but I have always had a stronger bond with my grandmother. My mother married my stepfather when I was 9 years old and he too has never hugged me or hardly talked to me about life told me he loved me as well. I have two brothers from their marriage and she’s always protecting them and she interacts with them and when it comes to me I was always left on my own. I feel bad at times because I don’t have a general love for my mother. She hugs my son all the time and does nice things for him but not really me.I never get the feeling where I want to hug her either. I am the total opposite with my son I love him up something awful, we sing and dance together and do silly stuff i shower him with so much love and affection because I never got that from my parents growing up.