'Game of Thrones': Fifth "Successor Show" in the Works at HBO, George R.R. Martin Says

George R.R. Martin took to his blog Sunday to provide some clarity about those Game of Thrones follow-up series that HBO is working on.

While Martin eliminated two popular theories for what some of the prequel series could be, the real news is that there's another writer working on a fifth potential offshoot of the beloved fantasy drama. 

"We had four scripts in development when I arrived in L.A. last week, but by the time I left we had five," Martin wrote on his LiveJournal page, declining to name the fifth writer.

HBO announced May 4 that there are four separate ideas being worked on by four different writers: Max Borenstein, Jane Goldman, Brian Helgeland and Carly Wray, with Martin connected to two of them. The author clarified that he is involved in all four (and presumably the fifth) as he has been in close communication with all five. (HBO did not immediately respond to comment for the name of the fifth writer.)

Of the four initial writers, not one has any current ties to the HBO Emmy winner. Game of Thrones showrunners Dan Weiss and David Benioff are not currently attached to write on any of the four efforts. The duo, however, will serve as executive producers on any of the four takes that move forward. Martin will serve in the same capacity as well. Weiss and Benioff are finishing up the seventh season of Thrones — set to bow July 16 — and are in the midst of writing and preparing for the eighth and final season of the fantasy drama series. Both will continue to be kept in the loop in all things Thrones.

Martin also clarified that he doesn't see any subsequent Game of Thrones series as a "spinoff," going so far as to note that he doesn't like the term and refers instead to them as "successor shows." He's also realistic that not all five of the ideas will move forward.

"I do think it's very unlikely that we'll be getting four (or five) series," he wrote. "At least not immediately. What we do have here is an order for four — now five — pilot scripts. How many pilots will be filmed, and how many series might come out of that, remains to be seen. (If we do get five series on the air, I might have to change my name to Dick Direwolf)."

Following the news of the "successor shows," many Game of Thrones experts — including THR's resident Westeros guru Josh Wigler — identified a few likely candidates from Martin's vast world that could be prime for TV, with two breaking out as the most popular theories:

Dunk and Egg: Ser Duncan the Tall and Aegon the Unlikely (aka Dunk and Egg), the duo at the heart of Martin's most prominent A Song of Ice and Fire spinoff — a series of novellas that include The Mystery Knight and The Hedge Knight. Many have speculated that Dunk's and Egg's eventual fiery deaths at the Targaryen stronghold known as Summerhall will have an important impact on the future of Thrones, which makes their story ripe for adaptation as a prequel.

Martin on Sunday clarified that neither Dunk and Egg nor Robert's Rebellion were among the five ideas currently being given the script treatment.

"We're not doing Dunk & Egg. Eventually, sure, I'd love that, and so would many of you. But I've only written and published three novellas to date, and there are at least seven or eight or 10 more I want to write," Martin said. "We all know how slow I am, and how fast a television show can move. I don't want to repeat what happened with Game of Thrones itself, where the show gets ahead of the books. When the day comes that I've finished telling all my tales of Dunk & Egg, then we'll do a TV show about them...but that day is still a long way off."

The second popular theory was Robert's Rebellion: The contentious civil war that nearly destroyed the Seven Kingdoms, and very much did destroy House Targaryen's reign over Westeros. It would be an opportunity to bring Robert Aramayo back as a young Ned Stark, a role he inhabited during season six of Game of Thrones, as well as younger versions of some other fan-favorite characters, including Jamie (Nikolaj Coster-Waldau) and Cersei Lannister (Lena Headey).

"We're not doing Robert's Rebellion either," Martin noted. "I know thousands of you want that, I know there's a petition...but by the time I finish writing A Song of Ice & Fire, you will know every important thing that happened in Robert's Rebellion. There would be no surprises or revelations left in such a show, just the acting out of conflicts whose resolutions you already know. That's not a story I want to tell just now; it would feel too much like a twice-told tale."

Click here for a closer look at the four writers who are working with Martin on the Thrones prequel.