Looking at Aenys' age, I'd say that Alyssa Velaryon was not from Daemon Velaryon's generation, nor from the generation after that, but from the generation that comes next.

I suppose Aerion married Valaena because he had no sister to wed, and Valaena was the next best thing: half Targaryen on her mothers side. Those are all the Velaryons in present times, but there is a huge gap between Alyn and Monford, I agree. Well, in the present asoiaf times, we have Aurane Waters, the bastard of Driftmark, with his trueborn brother Lord Monfrod, and Monfords young son Monterys. Perhaps could go a little back, to understand why Aerion married Velena Velaryon. Ran told that the parentage of Addam and Alyn would be discussed in the World Book, so I guess that opens up the possibility for more discussion on House Velaryon.Д®xacly! Since after Alyn the no other Velaryon is mentioned (or at least seems close to Targs) makes sense that this part of the family has something right by Targaryens. Nephews (who might not have been in Westeros during the Dance, because House Velaryon does use a lot of ships, perhaps they were gone on adveture?) or more distant cousins (who would then not necessarily live on Driftmark, and thus not been mentioned so far). What I think, is that there's simply a few Velaryons we haven't met yet. To marry Aegon, she would need to be old enough to birth Daeron in 143AC, which she couldn't have been if she was Alyn's daughter, and in addition, Elaena and Alyn would then be granddaughter and grandfather, not cousins, so this options is eliminated as well. In any case, to me it seems that Alyn and Addam were born to a man from Laenors generation, though not necessarily from Laenor himself.Дaenaera married a King, so being a bastard girl who is legitimized would be out of the question for her (so the possibility of Daenaera being Alyn's sister is gone). Though it seems unlikely that Alyn and Addam were children of Corlys (the young age, Corlys' love to his wife), it might be that he had nephews or cousins who had bastards. Thats the reason why I asked about the Velaryon family tree in the book, since we already know that Targs will be there (apart from Egg's time, spoiler on D&E) Maybe in 'The Rogue Prince' will they mention anything (thats why it was updated in the app)? The fact that Addam and Alyn are brothers by Laenor could open the possibility of Daenaera be their sister (I don't think so but just throwing some ideas)? However there is no evidence yet on where did she came from.

Would be cool to find out if Corlys really had a brother (or sister) and Daenaera was his niece. (royal claim and blood ties, were Daenaera wouldn't of had that if she was a niece or grand-niece.) So I figure, Corlys would rather have children of Laenor as his heirs, instead of Daenaera because one she's young, also female and thirdly Addam tames a Dragon and (if Laenor is his father) both he and Alyn are 1/4 Targaryen through Rhaenys. She'd be old enough to be Daeron et al's mother and, if Addam and Alyn are Leanor's it'd make Elaena Targaryen and Alyn 2nd cousins. If she was already born however, perhaps to a deceased younger brother of Corlys. Daeron is born in 142, Daenaera could only have been born in the early part of 131, at the earliest. Daenaera however, couldn't be Corlys daughter though, due to birth dates. I'm not certain about Alyssa, (shes a daughter or granddaughter of Daemon perhaps?).

Westeros family tree