The following post contains some spoilers, mostly for watchers of the TV show, so turn back now if you’re sensitive to such things.
So, some book readers have put together this theory through the trail of crumbs left by George R.R. Martin in the books.
There is already a popular fan theory out there, R+L=J – in spoiler form that translates to Rheagar Targaryen and Lyanna Stark are the parents of Jon Snow. This would mean Jon Snow is the super-mega king of all kings that everyone always knew he was, and the key to defeating The Others.
Here’s a handy video that explains it:
And here’s the new theory that’s now being bandied round: R+L=J+M, with M standing for Meera Reed, Bran Stark’s travelling companion.
Right, here’s where you need to be up to date with everything in the video.
The theory goes that at the battle at the Tower of Joy, where Ned Stark and an assortment of knights went to rescue Lyanna, Ned’s sister, from Rheagar Targaryen, everyone was killed except Ned and Howland Reed. Instead of Lyanna giving birth to just Jon, as the original theory goes, she gave birth to twins, with Meera being Jon’s brother.
Lyanna made Ned promise to look after them, so Ned took Jon and raised him at Winterfell, and Howland took Meera and raised her, both hiding their Targaryen identities.
Evidence-wise, there are a few clues that back up the theory. In both the books and the show Jon and Meera are the same age. They also both look extremely similar. And Crannogmen like the Reeds are usually small, like Meera’s brother Jojen, but she is depicted as being normal size.
With rumours going around that the next season will feature flash back scenes at the Tower of Joy, we could find out sooner than expected.