Frankly, this is a non-argument.
How about the 11th kid that was never born to a 10 child family? The one that would have found the cure for all forms of Cancer?
Or the 12th, who would have discovered Warp Drive?
There are an infinite number of children with an infinite number of possible lives for all married couples.
Or suffice it to say, I have never understood this particular argument for fecundity.
I guess you are correct.
After all, where were the mass murderes and serial killers, et al, in the order?