MrsMopp, just to say that not all g.children bring joy to the lives of the g.parents, any more than all AC bring joy to the lives of their parents.
Just remember how fortunate you are to have two sons, in good health and who have a good relationship with you.
No good mourning for a fantasy life that might-have-been. No guarantee that any g.child, had they existed, would have been totally healthy, would have kept in any sort of relationship with you, would not have caused you so much heart-ache and anxiety.
We have children (hopefully) because we want to be parents, not as some sort of future use of them to provide us with g.children.
Yes, I have g.children, I am fortunate that I have a reasonably good relationship with all their parents and with them. However, I can honestly say, that if none of my children had wanted their own children I would have been quite happy about that. Just want my children to be happy in all their choices in life.
When my children were small, I refused to be defined as 'Their Mother' - I insisted I remained a person in my own right. Equally, having g.children does not define me in any way.