Crude, but you are quite correct and you get an upvote, that was the sin in the GARDEN and a subject that mainstream Christianity does not want to touch with a ten foot pole, it is so politically incorrect, this subject like many others in the Scriptures get spritualized away by these lukewarm Christians. And there was never an apple.  Nonetheless, you likely already know that the child from this forbidden union was Cain via "SUPERFECUNDATION".  That is why Cain is NOT in the genealogy of ADAM and it is also why First John 3:12 tells us "Not as Cain who was of that WICKED ONE and slew his brother. Seth is the replacement to Abel who was slain and Seth is found exclusively in the genealogy of Adam. We also know that Cain and Abel were twins as they both came of age at the same time as they were expected to respect the blood sacrifice. Genesis 3:15 tells us the rest of that story especially when Bible teachers refuse to believe that Sataniel has little children or offspring on the earth.  "And I will put enmity (hate) between thee (Satan) and the woman and between thy (SATAN's) seed (Heb. ZERA=offspring) and her seed (Heb. ZERA=offspring.)  Lastly Matthew 13:38 tells us the rest of the story. "The field is the world; the good seed are the children of the kingdom; but the tares are the children of the WICKED ONE."  Jesus Christ then tells us in John 8:44 who these children of the wicked one are today.  "Ye are of your father the devil, and the lusts of your father ye will do. He was a murderer from the beginning and abode not in the truth, because there is no truth in him. When he speaketh a lie, he speaketh of his own: for he is a liar and the father of it."  The first murder recorded in Genesis was that committed by CAIN.  Yahshua (Jesus)Christ was quite specific about it.  Since you already know the truth, take comfort that the seed of the woman (offspring) did survive and are the same referred to in Genesis 3:15, the descendants found in Revelation 12:17 are referred to as the REMNANT OF HER SEED which keep the commandments of God and have the testimony of Jesus Christ. It was inevitable that the remnant of her seed are the good seed that became the first Christians and spread the Gospel throughout Arsareth (Europe) then the world.  God Bless you.