Who were Adam and Eve's first two sons?

Answer: Cain and Abel

Eve gave birth to Cain first, then Abel.

“And Adam had relations with his wife Eve, and she conceived and gave birth to Cain. “With the help of the LORD I have brought forth a man,” she said. Later she gave birth to Cain’s brother Abel. Now Abel was a keeper of sheep, while Cain was a tiller of the soil.”— Genesis 4:1-2 (BSB)