If you believe the Bible, then at least one of Adam and Eve's sons had to marry one of their daughters. Adam and Eve are the ancestors of all living humans (Gen. 3:20), which by definition means that the only women available at first would be sisters (in all likelihood, nieces would also become available to marry not long after the first sibling marriage).
Keep in mind that since the early humans lived up to around 900 years (about 10x modern age), and Adam had at least three sons by the time he was 130, if they averaged a child every other year until age 500 (which is conservative - Noah only got started at age 500), then Adam and Eve had 185 children - so "sister" would be genetically accurate, but relationally, you wouldn't think of them the same way we do.
Marrying siblings was not outlawed until Moses day - in the giving of the law (Lev. 20:17). Examples of marriages between close relations: Abraham married his half-sister Sarah - Gen. 20:12; Isaac married his cousin's daughter (Gen. 22:20-23); Jacob married his cousin (Gen. 29:10, 28); Moses' father married his aunt (Ex. 6:20).
In some religious texts, it is suggested that Abel did not marry before he was killed by his brother Cain. However, since details are limited, it is not explicitly stated whether Abel was married or not.
Adam is the father of Cain and Abel according to the Bible.
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cain was jealous that god had not accepted his sacrifice like he did with abel
Abel does not have a younger brother, he is infact the younger brother to Cain. Cain kills his younger brother, Abel.
Cain had no choice but to marry his sisters and have children.
In some religious texts, it is suggested that Abel did not marry before he was killed by his brother Cain. However, since details are limited, it is not explicitly stated whether Abel was married or not.
The sons had to marry their sisters. Adam and Eve were the only 2 people on the earth.
Probably a woman from the Land of Nod.
The bible mentions Seth, but not all the others. He either married a sister or a close relative.
According to the Bible, Cain married one of his sisters after being banished from the garden. It is commonly believed that Adam and Eve had other children besides Cain and Abel, so Cain would have married one of his sisters.
In the biblical story of Cain and Abel, Abel was killed by his brother Cain.
Cain and Abel were the sons of Adam and Eve. Cain killed his brother Abel out of jealousy and anger.
In the biblical story of the brothers, Cain killed Abel.
The cast of Abel and Cain - 2013 includes: Alex Bone as Abel, Cain, and Abel-Cain Tara Cioletti as Rachael, Lilith, and Rachael-Lilith
In the Bible, Cain killed his brother Abel.
Reading the scriptures carefully shows that Adam and Eve fathered Cain and " meanwhile they continued to have children" or similar words depending on the translation. If one takes the bible literally and not as a collection of stories, then the only logical answer is "He married one of his sisters"