has anyone noticed the increase in single parents and children only knowing a step-parent as father or mother?

I have a 16month old son who I am raising alone with the help of my parents due to abandonment by the father. For his own "up-bringing" reasons, age, and immaturity cannot handle this task. I have always felt an immense amount of pain knowing someday my son will ask for him, and i in return have nothing prepared to say. Anyway, i’m in nursing school and volunteered at an elementary clinic. As i looked through the contacts, i was surprised to see so many children with only the mother as contact, and sometimes even only a father. Half of these children lived in a single home, or with a step father, whom they now call dad. I was expecting to see depressed, sad, children. How affected are children by not having a father or mother ? Or dealing with a step-parent. I myself am fortunate to have both, but now i want to know what’s it like for those who were not raised with a father or mother. Did it make you stronger? insecure? How did your mother/father explain this to you as a child. thanks. i have been stressing so much and been depressed over this for so long, sometimes even blaming myself. But now i see that i am not alone!