Sometimes the more interesting number is the span between the first one and the last one. Certainly is in my mother's case. (Not including my Dad in this because he died young. He only knew 3 of his grandchildren, but there are at total of 6. Besides that, men naturally tend to have a longer run at the parenthood game if they marry multiple times (though neither of my parents did; all of the children they had were theirs together.) Looking at the female line is far more instructive.))
My parents' first grandchild was born in 1962 (when they were 48 & 50), and the final one in 2007. That just about doubles the range from the first to final time they became parents: 1940-1962.
Being as I'm the youngest and now in my late 50's, and that my eldest dislikes children, I don't expect either of my children to have children in my lifetime.