Starting with Genesis chapter 4 - God put a curse on Cain to be a wanderer. Cane appeal to the Lord, Cain was scared that ANYONE finding him may kill him _ who are the "anyone" if there are only two offsprings of Adam and Eve - now one because Cain slew Abel. And God said NO ONE should touch Cain - no one?
That scripture implies there were other adult people around.
The teachings of the church is Cain and Abel were the first two children born to Adam and Eve and they had daughters afterwards and Cain married one of those daughters - which would make him and her brother and sister.
Yet scripture tells us God said don't marry your brother, sister, mother, father, aunt, uncle. Why is that since we were all created to commit incest anyway? THE TREE OF LIFE - it's healing effects gave man a form of immortality and CLEANSED the BLOOD. After the fall of Adam the Tree of Life was taken away and everyone born was born in sin, under of the penalty of death of the flesh.
Different understandings beginning to surface
The Tree of Life is the key.
Descendants of Adam before he sinned was cleansed by the fruit and leaves of the Tree of Life.
Now there is no where in scripture that indicates when Adam sinned or whether he had children before he sinned. God's commandment to them was to be fruitful and multiply and replenish the Earth, before their fall.
AND
There are also indications that Adam did have children before he sinned _ Cain went to the Land of Nod and knew his wife. Who lived in the Land of Nod? The church teaches the name is symbolic - a easy way to get out of giving an explanation. The Bible didn't say Cain took his wife or Cain and his wife went - yet he went to the Land of Nod before he knew her.
There is more than one way to interpret what scripture actually means when it says Adam's sin brought death into the world, and death fell upon all mankind. And that interpretation would be based on the Tree of Life and God saying that he put them out of the garden so that they wouldn't eat from it and live forever. Church will teach that they never ate from the Tree of Life, yet God put it in the garden and told them they could eat from every tree except the Tree of Knowledge - convenient reasoning to keep from explaining.
Far too many churches today teach that it is just symbolic - yet all the medicines of mankind basically comes from greenery. In the Book of Revelations it clearly states the Trees of Life is on each side of the river, on the new Earth, that has no oceans or seas or night. There are 12 different fruits, new every month and the leaves are for the "healing" of the Nations and our Lord God is there and is the light thereof.
Did Eve Have Children Before the Fall?
The female Cain married was an offspring of Adam but through the cleansing of the Tree of Life no longer considered Cain's biological sister - even as mankind consider themselves today "none are considered biological sisters and brothers except through direct mother and father."
I read where it has been taught throughout the centuries in just about all churches Adam and Eve were unable to procreate before the fall - that doesn't make sense because God's commandment was given to them before the fall to be fruitful multiply and replenish the Earth so why wouldn't they be able to procreate before their fall?
People of today, especially today - fail to realize that the writers from thousands of years ago did not write in the same manner as the educated people of today. They were just learning to write, the majority of the people didn't read or write - even up until the 18th century AD.
That is a lot to say just to say we are all offsprings of Adam, which means we are all sisters and brothers - yet not biologically _ nor was the female Cain married his biological sister and maybe to be politically / literally correct I should say immediate biologically.