They are not exactly Cain and Abel, but theologically and philosophically Christopher and Peter Hitchens are just as divided as the brothers of the Old Testament.
Christopher Hitchens, 61, author of the bestselling book "God is Not Great," is one of the world's best-known atheists. Peter Hitchens, two years younger, is not as well-known, but he is also an author, and a devout member of the Church of England.
Estranged for years until very recently, the Hitchens brothers have just released books within days of each other.
Christopher's book is his memoir, titled "Hitch 22."
Peter's book, as well, is a memoir of sorts. "The Rage Against God: How Atheism Led Me to Faith" chronicles his journey from radical atheist to faithful servant of God, and in so doing has put into written form his ongoing heated debate with his brother.
Peter says of Christopher, "He dislikes anybody believing in what he describes as the supernatural."
Peter also has no illusions that his faith may have any profound influence on his brother.
"Part of my reasons for writing this book was not to get my brother to get to the altar, or to get him to be a Christian, which I think is a sort of a ridiculous and hopeless task certainly beyond me," he writes. "What I did want him to do was to stop the hostility and sneering that faith is possible."
He continues with a more general critique of the "New Atheists," chiding them for "[t]he way in which they treat Christian believers as stupid, and belief as a form of stupidity and their unwillingness to accept that other people might have come to a different conclusion from them, through intelligence and reason."
Christopher had intended to be interviewed for this article, but he cancelled at the last minute because of an emergency. But he said in a 2008 debate with his brother that "I think there's no reason to believe in the absurd proposition," meaning belief in God.
"It's a totalitarian belief," Christopher said. "It is the wish to be a slave."
How brothers raised in the same household could have such disparate worldviews on faith puzzles even Peter. He and Christopher are intellectual equals, possessed of the same gift of glib wordplay, which makes their debates entertaining, at least.
But one event that Christopher writes about in his memoir had a profound effect on him: their mother's suicide in 1973 in a hotel room in Athens.
Peter won't speculate much about how that may have affected his brother, saying, "I made the decision not to talk about that in detail." But he does say that "one of the major differences is that he went to Athens where it took place, where I stayed home with my father. Therefore he saw in detail what happened in a way that I didn't.
"He told me details later. But that must have had a much greater effect. The far deeper impact in talking to the police and coroners about what they found and hearing it first hand must have a terrible impact. The death of a parent is an enormous thing. It has to have a huge effect on you."
Peter won't say what brought Christopher to such a ravenous contempt for belief in a supreme being. But he says his own atheism took the form of "a rambunctious, arrogant, annoying teenager who thought he knew everything." He says finding faith in the religion of his youth was a slow process befitting an Englishman's reserve. There were no "aha!" moments, no pious revelations. Just the end of a long, rational road that refused to yield what he had believed it would.
"What happened to me was that I got there, I thought it was the final station and I discovered that it wasn't," he says. Peter says that when he took atheism to its logical conclusion, he found that "what was at the end of the tunnel was so unattractive that it seemed to me to be right to consider everything." And "everything," he says, meant a return to where he started -- to his childhood, to Christianity, to what he had been brought up to believe.
Why Christopher didn't make the same journey is for him alone to say. His animosity toward anything religious is well documented in his books and speeches.
Does Peter hope or pray for his brother?
"Believing what I believe and thinking what I think," he says, "it would be wrong of me not to hope.
"I think anything is possible. But it's not for me to speculate."