I checked out William Branham's teaching on SS after I was told he said some people are the seed of the Serpent (as a result of the sexual union between Eve and the Serpent) and they cannot be saved, while others are the seed of Adam, and they will be saved. I found out that's not what he said at all. Yes, he did say the original sin was adultery, but nowhere did he teach that salvation is anything to do with race or genetic ancestry.
I think the best understanding of what he did say is found in his book "An Exposition of the Seven Church Ages" - the comments contained in this book can be easily found by entering the words
serpent and
seed in 'Message Search' at the Voice of God Recordings website.
I did not find this idea too remarkable - perhaps because I had heard some Pentecostal ministers teaching that the "sons of God" in
Genesis 6:4 were heavenly angels who had sexual relations with human women and produced children who grew up to become giants. Personally, I think there is more Biblical support for William Branham's idea.
And I think we should keep in mind this comment he made about SS:
"Course we realize that that doesn't save a man, neither does it condemn a man, but it only brings light upon the subject"