How much time is this? How old were they, did they already have a family of their own. The bible uses the term 'in the course of time' ( Gen 4:3). We know that ' Abel kept flocks and Cain worked the soil' ( Gen 4:2). There had to have been a passage of time between their (Cain and Abel) birth and when Cain killed Abel. I am trying to establish the population growth which is needed to establish what would happen later when Abel was killed and Cain banished to the land of Nod. They (Cain and Abel) were 20 years of age. So, I have Cain and Abel's first born having children at their age 10 (their first grandchildren). Also during those ten years, Adam and Eve were still having more children. If we assume Cain and Abel were a set of quadruplets with two (2) sisters also born at the same time we can say Cain and Abel were able to have children at the age of ten. So, lets say both males and females bodies were fertile by the age of 10 and able to conceive.

To further this command, they had to lie with their sisters to accomplish this. Lets get back to the 'be fruitful and increase in number' (Gen 1:28). Lets, again postulate, that in those days of beginnings, God made them very fertile and with remarkable health to be able to conceive at a rather accelerated pace especially in the beginning. So, let me pause here and entertain the following. Either Cain and Abel were twins or perhaps quadruplets with other sisters born at the same time and Eve continued to have children (males and females) as quickly as possible to fulfill Gods command (Gen 1:28) or they were born within a year or so of each other. I will further postulate that in the beginning Eve was giving birth to more than one child at a time, by that I mean twins, triplets or even more as rapidly as her body was able to recover from pregnancies. So, again, I will postulate they were born within the first year after Eve ate of the forbidden fruit and banished from Eden. So, I will postulate, that Seth and Abel and there also had to have been sisters born rather quickly in order for this population of the earth to happen. God blessed them (Adam and Eve) and said to them, 'Be fruitful and increase in number' (Gen 1:28). Seth, was born when Adam was 130 years old (Gen 5:3). But, that does not necessarily mean they were the first three males born to Adam and Eve. We know they are mentioned by name in the bible. I am trying to come to a reasonable conclusion concerning Cain, Abel and Seth.

Cain and abel meme