It isn’t always one egg at a time! You do realize that multiples are not always identical, right?
Yes, but they are not the “norm”. It’s not like a younger woman has a better chance of getting pregnant because she releases a dozen eggs a month, and later they are almost all gone so she only releases one a month.
So I don’t understand how the number of eggs left in her ovaries can effect the ability to get pregnant in any particular month.
My grandmother and her twin brother were not identical twins.