By now you've probably caught up to the last episode of Game of Thrones season 6, and if you've not, then turn around, or read on because you deserve reading some spoilers. Everyone knows Jon Snow is an illegitimate child, but what is his birth name?

The R+L=J theory was confirmed on the season 6 finale.

So, now we know he's definitely Rhaegar Targaryen and Lyanna Stark's son.

When Lyanna whispered into Ned's ears, it all but seem inaudible. She definitely did not say that "Jon" was his name. Check it out:

Redditor sparkledavisjr has a theory as to Jon’s real name.

“Lyanna starts by whispering ‘His name is,’ and then what follows appears to be a three syllable word that appears to start with a J,” wrote sparkledavisjr. “I’m not a great lip-reader, but I’m fairly certain what she says is Jaehaerys.”

The name seems probable because..

Jaehaerys I was the 4th Targaryen king to sit the Iron Throne. He was known as ‘the Wise,’ ‘the Conciliator,’ and ‘the Old King.’ His long rule was prosperous and he was aided by his sister-wife Alysanne, who convinced Jaehaerys to expand the Night’s Watch and granted them the land now known as the New Gift.

Jaehaerys II was Jon’s great-grandfather. His reign was short due to his ill-health (only three years), but still a good one. Jaehaerys restored stability to the realm, ended the Blackfyre threat during the war of the Ninepenny kings, and improved relations with the major houses who were unhappy during his father’s rule (Aegon V — Egg, the brother of Maester Aemon).

If Lyanna was in love with Rhaegar (as seems likely), it makes sense for their son to have a Targaryen traditional name like his siblings Aegon and Rhaenys. Jaehaerys would be a good pick as the name isn’t associated with any real negative connotations, like Aerys, Maegor, etc.

Will he change his name?