Just don't overthink. Writers are just bad and lazy. Don't expect Martin's plots, or even something with a little bit of sense here. I mean, even the NK didn't have anything to cross the wall without the dragon so, they were heading north just for the laughs i guess.
So, now, Viserys's lost twin married Lyanna and named his son Aegon? same as his other son? i imagine them, come on, Aegon number 1, leave number 2 alone...
Writers are so DUMB. I liked Jaehaerys more...