Although we know that Jon Snow is the son of Lyanna Stark and Rhaegar Targaryen, there is still much to discover about this, one of the most important characters in Game of Thrones.
According to a supposed page in Empire magazine, besides knowing its origin, Bran knows the name of Jon, which would be Jaehaerys Targaryen; Just like one of the great kings of Westeros, who was known as "The Wise."
In addition to validating his status as a legitimate heir to the Iron Throne, it is believed that this would be the definitive proof that Jon is the hero of whom the legends speak, the one who in the end will save that world from the whip of the White Walkers.