OMG so now Cain is the devil's son and not Adams? Where do you people get this garbage. Not even close to scripture and teaching those that dont know better a lie is very dangerous, Yehoveh wont be giving false teachers a break.

Sherry is does not matter what you or I believe.

This is what they believe.

It comes from a misunderstanding about scripture. I've heard this several times and looked into it but never found the proof that people say was proof. Actually what I found was the opposite. If Cain was Satan's seed, the Lord would not have had this conversation with him;

Verse 6 "Then the Lord said to Cain, “Why are you angry? Why is your face downcast? 7 If you do what is right, will you not be accepted? But if you do not do what is right, sin is crouching at your door; it desires to have you, but you must rule over it.”
After Cain was driven from the land, there was this conversation:
15 But the Lord said to him, “Not so[e]; anyone who kills Cain will suffer vengeance seven times over.” Then the Lord put a mark on Cain so that no one who found him would kill him. 16 So Cain went out from the Lord’s presence and lived in the land of Nod,[f] east of Eden.

This is NOT the conversation the Lord would have had with Satan's seed. Satan had already been cursed.