While some years a go there was a claim that Martin had said (in a mail to an individual who reported on the GeorgeRRMartin mailing list) that Aegon was dead, the exact wording of this statement was never produced and the reporter could not vouch that he had correctly interpreted GRRM’s statement to him. Since then, GRRM has been cagier about the issue. For example, when asked about the fates of both of Rhaegar’s children, he only provided a definitive answer concerning Rhaenys’s fate (SSC). When probed further about Aegon, his answer was rather coy (SSC).

The popular theory as to why Aegon is not dead is that he was spirited out of the Red Keep at some point, and replaced with another baby who looked somewhat similar (not the easiest thing to do, since Aegon was coming out more Valyrian, but presumably any child with fair hair and blue eyes would probably pass inspection by the likes of Ser Gregor Clegane). It’s usually thought that if this was the case that Varys would be responsible for it. Candidates for who Aegon may now be are many, and include Samwell (too old, in fact), Edric Dayne (too young), an as-yet-unnamed child residing with Howland Reed in the Neck (speculation based on metaphorical analysis of the text), or someone else entirely. No definitive answers can be made at this point in time.

The reason why some feel that Aegon must have survived include Rhaegar’s definitive statement that Aegon was the prince who was promised and that the dragon has three heads (II: 512). Martin has noted, however, that one does not necessarily have to be a Targaryen to be one of the three heads (SSR).