Did Adam and Eve's sons have a sister, or did they reproduce with their mother instead?

Adam and eve had sons and daughters (Genesis 5:3). I don't know where people are getting "twins" or exactly how many kids they had. We know the names of three of their sons, (Cain, Abel, and Seth). They probably had sex with their sisters and, well, who the heck knows. They might have done it with Eve, too.

There were other people on the Earth. Adam and Eve were the only 2 created in the garden. Cain's wife came from the Country called Nod. Both Adam and Cain were builders of cities. It takes at least 10 families to qualify as a city.

Concept that Adam and Eve had only two children is wrong. They had two sons and two daughters. One daughter and One Son being born at the same time as twins. So there were two pairs of twins. Members of one twin pair married the ones from the second twin pair and hence the generation continued. Quran clearly mentions the birth of twins at many places. Although, coming together of siblings may seem like incest, it was allowed at that time and only later was it made a sin.

Adam and Eve had many many children. They formed tribes and God and His angels helped them not to incest.

There were people that lived outside the garden too

God made a variety of people, Adam and Eve were Chosen just like Abraham was Chosen.

But I did hear that we all have some DNA that relates to everyone, so who knows for sure?

Genesis 5:4 acknowledges that during his life, Adam “became father to sons and daughters.”

Do you think God made one stalk of wheat or one blue jay?

You have NO business reading scripture.

Here's a warning from the God you don't believe in.... it shouldn't bother you.... cuz he's not real, right?

To the wicked, God says:

“What right have you to recite my laws

or take my covenant on your lips?

You hate my instruction

and cast my words behind you.

When you see a thief, you join with him;

you throw in your lot with adulterers.

You use your mouth for evil

and harness your tongue to deceit.

You sit and testify against your brother

and slander your own mother’s son.

When you did these things and I kept silent,

you thought I was exactly like you.

But I now arraign you

and set my accusations before you.

“Consider this, you who forget God,

or I will tear you to pieces, with no one to rescue you:

Those who sacrifice thank offerings honor me,

and to the blameless I will show my salvation.”

Your obsession is a window into your insecurities. Very sad to be you. And you're very slow to understand too..... God doesn't care if you believe or not. He can raise children for Abraham from the rocks.

You disown him, he WILL disown you. Simple

It is likely that God introduced many more humans into the world after Adam and eve. Derp.

Cain and Abel had hot sweaty sex with their mom.

Hates gays...but loves incest...and rape...and slavery...and killing...etc.