Moses
Genesis 4:2ESV·traditional attribution

And again, she bore his brother Abel. Now Abel was a keeper of sheep, and Cain a worker of the ground.

John Calvin Reformed @genevareformer

2. And she again bare his brother Abel “Et addidit parere fratrem ejus Ebel;” and she added to bring forth (or she brought forth in addition) his brother Abel. — Ed. It is well known whence the name of Cain is deduced, and for what reason it was given to him.

Matthew Henry Presbyterian @wholebiblehenry

Adam and Eve had many sons and daughters, Gen 5:4. But Cain and Abel seem to have been the two eldest. Some think they were twins, and, as Esau and Jacob, the elder hated and the younger loved. Though God had cast our first parents out of paradise, he did not write them childless; but, to show that he had other blessings in store for...

Commenting on Genesis 4:1-2

John Gill Reformed Baptist @doctorgill

And she again bare his brother Abel,.... Or "added to bare" (y), not directly or immediately, but perhaps the following year; though some have thought, because no mention is made of her conceiving again, that she brought forth Abel at the same time she did Cain, or that the birth of the one immediately followed upon that of the other: and it is the common...