Eve was made for Adam out of Adam’s rib.
Genesis 2:18 And the LORD God said, It is not good that the man should be alone; I will make him an help meet for him… 21 And the LORD God caused a deep sleep to fall upon Adam, and he slept: and he took one of his ribs, and closed up the flesh instead thereof; 22 And the rib, which the LORD God had taken from man, made he a woman, and brought her unto the man. 23 And Adam said, This is now bone of my bones, and flesh of my flesh: she shall be called Woman, because she was taken out of Man.
All people are descended from Adam and Eve.
Genesis 3:20 And Adam called his wife’s name Eve; because she was the mother of all living.
The children of Adam and Eve would have married their brothers or sisters.
Genesis 5:4 And the days of Adam after he had begotten Seth were eight hundred years: and he begat sons and daughters:
There were no other families.
We all die because we are descended from Adam and Eve.
Romans 5:12 Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned:
Romans 5:17 For if by one man’s offence death reigned by one; much more they which receive abundance of grace and of the gift of righteousness shall reign in life by one, Jesus Christ.) 18 Therefore as by the offence of one judgment came upon all men to condemnation; even so by the righteousness of one the free gift came upon all men unto justification of life. 19 For as by one man’s disobedience many were made sinners…
1 Corinthians 15:22 For as in Adam all die, even so in Christ shall all be made alive.
Only by believing and obeying the gospel preached by Jesus Christ and his apostles can we be saved from sin and death.
May I suggest that you read:
Your Share in God's Promises: https://www.thisisyourbible.com/library/show/181
I hope this helps