^ one thing I would like to add to above is that a child can only miss his/her parent when there is a good and positive memory attached to the parent. A child won't miss a parent who constantly abuse him/her both physically & mentally and also his/her mother. Children who see their mothers being abused do carry negative and angry feelings towards their fathers no child in this world like to see his/her mother cry or being beaten up.
Like Reha said every situation is different. In the example I have mentioned the main reason for the boy to become what he did was not his parents separation but the severe beatings he and his mother was subject to by his father. A healthy , secured and loving environment is very important for a kid . A child who lives under constant fear for him/her self and for his mother can not be a happy child.
So what's the lesser evil here? Divorcing when the kid is too young to understand (like baby/toddler age) and are thus "used" to their life, when they're old enough to understand but not realy (schoolage) or preteens/teens/adulthood?
Divorce is an ugly ugly thing and I sincerely pray that nobody ever has to go through it...ever.
My experience with divorce, I had to deal with my 2 children of different age groups. As it stands today, it is infinitely easier with my child who was a baby at the time rather than the one who was old enough to understand....under condition that ...i kept all the bitterness out of my heart. Both of them are free to talk about him, in fact if they havent mentioned him in a while, i make a small mention as a reminder to them.
I know the scenario will change as the younger one will grow up to ask more questions and more difficult ones too. I guess I will handle it when the time comes. But for now she feels loved by him, although she never sees him, simply because we talk about him on and off. I could never break her heart by making her think bad thoughts about him.