Game of Thrones author George RR Martin has announced he will be publishing a short story later this year set in the same world that catapulted him into the international spotlight.

The Sons of the Dragon will appear in an anthology called The Book of Swords, due to be released in October. Other renowned fantasy authors to appear in the book include Garth Nix and Robin Hobb.

Martin has said Game of Thrones fans will love the short story, particularly if they are "fascinated by the politics of Westeros".

"The Sons of the Dragon chronicles the reigns of the second and third Targaryen kings ... along with their mothers, wives, sisters, children, friends, enemies, and rivals," Martin wrote on his blog.

"[It is] a history rather than a traditional narrative."

The announcement comes at a curious time. Rumours have been swirling for months that HBO will be looking to capitalise on the cash cow that is Game of Thrones, with a backstory more likely than a sequel.

Just last month, HBO's programming president Casey Bloys told Entertainment Weekly a prequel would involve "less pressure" than a spin-off series.

"It's such a big property we would be foolish not to explore it, but it's a pretty high bar," he said. "We'll take some shots at it. I'm not going to do it just to do it. It has to feel very special."

Martin has said the new short story will involve "a lot of telling, only a little showing", meaning there is bound to be some flexibility there for producers to run wild and make the characters and smaller plot points their own.

In addition, the story will revolve around two dragon-riding ancestors of fan-favourite Daenerys Targaryn, Maegor and Aenys.

But before you get too excited, consider this: Maegor and Aenys aren't close relatives of Daenerys. They're not even her great-great grandparents.

To be precise, Aenys is Daenerys' great, great, great, great, great, (take a breath) great, great, great, great grandfather. Maegor, meanwhile, is Aenys' half-brother.

It's hard to imagine showrunners opting for such a distant prequel, when the events immediately prior to Game of Thrones are up for grabs. But at this early stage, nothing can be ruled in or out.

Season seven of Game of Thrones is due out in April. Emilia Clarke, who plays Daenerys in the award-winning series, took to Instagram over the weekend to label the latest instalment a "mind blower".

The Book of Swords is due to be released on October 10.