Talmudic tradition is that they were born before Adam and Eve sinned. However, God's decree after the sin included mankind in general, so Cain and Abel weren't excepted.
No, if you read Genesis 3:22-Genesis 4:2,it becomes clear that the birth of Cain and Abel (likely born at the same time as twins), were born AFTER God drove Adam and Eve from the garden of Eden, because of their sin.
26 verses, Expelled from Eden. Cain, Abel, Abel murdered, Cain's offspring, Seth.
The evidence of the Genesis account suggests that Cain was conceived [Genesis 4] after the "serpent incident" and Adam and Eve's subsequent banishment from the Garden of Eden [chapter 3].
The story of Cain and Abel and the story of Adam and Eve
Cain was the tiller of the ground, fulfilling the role that God promised for Adam in chapter 3, when he drove Adam out of the Garden of Eden. Then, in spite of Cain's generous offering, God refused his sacrifice. Some see the story of Cain and Abel as based on an Egyptian antecedent, a biblical countermyth to the story of Osiris and his brother Seth.
Cain was a tiller of the ground, fulfilling the role that God promised for Adam in chapter 3, when he drove Adam out of the Garden of Eden. He made an offering of his crop to God Then, in spite of Cain's generous offering, God refused his sacrifice and showed a clear preference for the offering made by his younger brother, Abel.
first of all i would like to say the Bible did not in clear terms record anything of the sort, and looking at the story of Cain and Abel in the Bible critically one can say that Abel was yet to get married at the time he was murdered by Cain and such had no issue and\or Child.
According to the Bible, Cain went to the land of Nod after killing his brother Abel. "And Cain went out from the presence of the LORD, and dwelt in the land of Nod, on the east of Eden." - Genesis 4:16
The Garden of Eden is described in Genesis chapters 2 and 3. Genesis 4:16 tells that Cain was exiled to a place of wandering (land of Nod) in the east of Eden.
Adam was cast out of Eden into an unsubdued earth that was cursed to produce thorns and thistles, there to sweat out an existence, harvesting the bitter fruits of his sin. Outside the garden, awaiting death, Adam fathered sons and daughters, the names of only three being preserved-Cain, Abel, and Seth.
The theme of the story of Adam and Eve is the interplay of joy, love, and sorrow in human lives. The love is shown by God's creation of the couple, and of the couple's enduring love for each other. The joy is shown in the couple's experience in the Garden of Eden, and in the birth of their children and their descendants. The sorrow is shown in the couple's expulsion from Eden, in the killing of their son Abel by their son Cain, and in Cain's running away.
According to Christianity, "Original Sin" begins in Genesis chapter 3. Eve, according to the story was tempted by a clever serpent to eat the fruit of the Tree of Good and Evil. This occured in the Biblical paradise called Eden. Shortly thereafter, Adam and Eve were expelled by God from Eden and set to toil in the earth (gardening). Later on their two sons, Cain and Abel gave offerings from their respected farm profession: Cain was a tiller of the ground; he grew vegetables. Abel raised sheep (Genesis 4:2-12). Anyway, each brother offered their first 'fruits', Cain his vegetables and Abel his sheep. God chose Abel's sheep over Cain's veggies. Cain grew angry with Abel and murdered his brother. God was infuriated and banished Cain to the land of Nod, east of Eden. These are only the beginnings of sin in Genesis. More goes on throughout Genesis in the flood story, the Tower of Babel, and on and on.