Why Did Natural Mother keep her girls and give her Boys away?

Why did She keep her Girls and Give her Boys Away? He writes, since meeting my Biological Mother / Sisters and Brothers, although many discussions in the earlier years With my Eldest Sister, my Mother has not once told me why. She has not officially told me who my Natrual Father is. In fact she gave me about four different persons who could be my Father. Including believing that I had the same Father as my Eldest Sister, that of what was told by the Mother on Adoption Application, after forensic test were done at our expense, he was not my Father. When I went and told my Mother this, she gave me some more names, but not once looked in my face. Why did she keep the Girls and give away her Boys? She is the only one that knows this I think. Trying to speak to some of her Sisters and Brother was not helpful, although they did appear to want to help. Ironically, at the beginning, we also found out that The Mothers Sister also Adopted a Boy out in the same year. I remember thinking and meeting her Sister who could have been my Mother but she wasn't. That Little boy is still out there.. Hopefully safe and Happy. THOUGHTS; Will the Mother ever tell the Little Boy/Adult who is his Father. And will she ever just sit down with him and have a chat? We will find out.