If the other person does mention his family, then it is perfectly OK to ask about the ages of the children, and if you have children, to compare educational and cultural differences in raising children.
Japanese children watch television more than English children.
Our children are anxious to have bicycles like those of the children next door.
Do you have any children?
He has no children.
As children are known to emulate the values of adults, it is often pointed out such "education mamas" instill a warped sense of values in their children.
Few children were in the room.
The higher the ratio of children to parents, the harder it is to bring up the children.
How old are your children?
Has he any children?
He hasn't any children.
That novel isn't for children.
It's true that there are fewer children due to the falling birthrate, and there are fewer children in the school, but that is all to the good.
I don't have any children.
As these days most parents indulge their children, many children don't know what good manners are.