While this plot line is still unfinished in the books, the TV show did not choose to open up this story.
If the HBO did open this narrative hook, however, would Jon and Daenerys have found yet another foe on their hands?
Aegon is described as an entitled but powerful person, who knows he is due to return and reclaim Westeros for himself.
Considering he is older than Jon, he has a better claim to the throne over him; and as a male, he immediately outranked Daenerys for her path to the throne, as well.
source: express.co.uk