Genesis 4:1

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 them, he preserved to them the benefit of that first blessing of increase. Though they were sinners, nay, though they felt the humiliation and sorrow of penitents, they did not write themselves comfortless, having the promise of a Saviour to support themselves with. We have here, I. The names of their two sons. 1. Cain signifies possession; for Eve, when she bore him, said with joy, and thankfulness, and great expectation, I have gotten a man from the Lord. Observe, Children are God's gifts, and he must be acknowledged in the building up of our families. It doubles and sanctifies our comfort in them when we see them coming to us from the hand of God, who will not forsake the works and gifts of his own hand. Though Eve bore him with the sorrows that were the consequence of sin, yet she did not lose the sense of the mercy in her pains. Comforts, though alloyed, are more than we deserve; and therefore our complaints must not drown our thanksgivings.

— Matthew Henry's Concise Commentary (public domain)