It seems like you're referring to the book of Genesis, specifically Genesis 4, which discusses the beginning of humanity's journey outside of Eden.
Adam and Eve started a family, they were married, having a child. It is important to understand that this was a marriage and it is the biblical model for marriage. When a man and woman leave their families and become one. Even in Genesis 2:24, we see the following: Therefore a man will leave his father and his mother, and will join with his wife, and they will be one flesh.
Let us pray together for those seeking a spouse, for a God-honoring marriage. Let us remember that sexual intercourse is intended for marriage, not outside of it. Hebrews 13:4 reminds us, "Let marriage be held in honor among all, and let the marriage bed be undefiled, for God will judge the adulterer and all the sexually immoral."
We pray this in Jesus Christ's name, the only way to access God. As it is written in Acts 4:12, "There is salvation in no one else, for there is no other name under heaven given to men, by which we must be saved."
To those who are currently in a relationship that does not align with biblical principles, we encourage you to seek God's will for your life. Pray for discernment and courage to make changes that honor God. God promises us in Matthew 6:33, to "seek first God's Kingdom, and his righteousness; and all these things will be given to you as well."