Yes, in the continuity of the television series and underlying planned lore, Jon Snow's true birth name given by his mother Lyanna Stark is Aegon Targaryen. While he was raised under the false identity of Ned Stark's bastard son to protect him from the wrath of Robert Baratheon, high-ranking revelations by Bran Stark and Samwell Tarly prove that he is the legitimate son of Rhaegar Targaryen, making him a true heir to the dynasty.