Game of Thrones: Series co-producer Bryan Cogman and George RR Martin are working on fifth successor series

Not four, but there are five Game of Thrones spin-offs are in works at HBO

According to The Hollywood Reporter, Bryan Cogman, a co-executive producer and writer on Game of Thrones since season one, is currently working alongside author George RR Martin on developing a new series set within the world of the Seven Kingdoms.

Details on the story are under wraps, though it's been said that all of the potential follow-up series in development will take place before the events of Game of Thrones.

Cogman wrote the season-four episode Oathkeeper, which featured one of the most jarring moments of the series for fans of the books.

The episode introduced the fans to the fearsome Night King for the very first time.

HBO's decision to develop multiple successors to Thrones comes as the pay cabler prepares to say goodbye to its most-watched series.

There are just six new episodes left of the big-budget fantasy epic. It remains unclear when that final season will air.

Although, GOT showrunners David Benioff and Dan Weiss are not involved in any of the potential prequels.