More to the point of the original post ...
My wife and I married relatively late in life for both of us. After we were married three years, our son was born ... he is just over 13 years old now.
We have our

moments with him, particularly now that he is entering his teen years, but I would not change things for the world - I am very happy and glad that he is here in it!
My wife and I ended up deciding not to have more kids some years after he was born - concern about birth or child problems escalates when a woman reaches a certain age (but can still get pregnant), and we chose not to go through the possibility.
However, in retrospect, we sometimes think we should/could have had another child ... both my wife and I had only two siblings each (very small for our generation and culture), and we get along with them great. Anyway, having a brother or sister is an experience that our son will not get to enjoy now - we are also past the child-bearing and rearing age ... probably too old to adopt now as well.
Z