(I love this line of discussion.)
When Adam was created, and then Eve, God told them, “Be fruitful and multiply and fill the earth...” (Gen. 1:28) This was before the fall, before any thought of disobeying the Father.
Adam was an absolutely perfectly functioning man, and Eve was a perfectly functioning female. Both were under command to Be Fruitful and Multiply.
Now, why in the (new) world would they neglect this prime directive until after they were cast out into the wilderness, out of favor with God?
Everything about the first two chapters of Genesis indicates that Eden should have been Crawling (literally) with kids and grandkids and so on. A perfect man and a perfect woman in a perfect enfironment with direct orders to go for it??!
Besides, there’s the point of Cain’s wife and enough people for him to found a city.
I honestly believe that Adam and Eve had lots of perfect, exciting sex and babies (with no labor pains.)
Just because they aren’t named and numbered doesn’t mean they weren’t there.