Cosmic

One thing I noticed about the Summer Islands is that they seem to have a healthy diaspora, not just in King’s Landing but in Braavos - Arya mentions Bellegere Otherys still resembling a Summer Islander despite it being several generations since Bellegere Otherys the First. It also seems like there’s Summer Islanders that live long term in Braavos; there's 50 Summer Islanders in the Golden Company, Arya mentions seeing many Summer Islanders, and Sam and Gilly travel on a boat crewed largely by Summer Islanders. This all makes sense world building wise - they're a culture of seafarers and we usually see them at large hubs like King's Landing and Braavos.

So really, folding show canon Corlys into book canon is incredibly easy when you think about the high number of Summer Islanders at port cities. My thought here is - Corlys is a proud man and very insistent on how he built his own fortune, both in the show and in the books. I thought of the type of parents he could have had and settled on a man who becomes angered at the comments he and his mother get for being darker skinned and Essosi/Summer Islander and deciding to just double down by marrying a rich Braavosi Summer Islander. So first Daemon meets a Sumemr Isles princess on his own travels, Salata Xam, and falls in love, then Corwyn, like Corlys, attempts to build a fortune through his own accomplishments, including his marriage to the rich Sarissa Jaedosys, and passes that stubborn streak onto his son.

Then, similar to how Sybell uses her new connections to get her brother some land (though he’s still kinda fucked there lol), and the Lyseni Spring, the House of Jaedosys ("jaedos" means "summer" in Valyrian, so while the family is Braavosi and has considered themselves Braavosi for some time, their house name is a reference to their origins in the Summer Isles) uses their new connection in Westeros to build their own fortunes up as well. Corwyn’s (canon) brother, Victor marries a cousin of Sarissa's, Doreah Jaedosys. In canon, Daemon and Corwyn have several children - Daemon’s names here are all canon (AND he has some daughters), and Corwyn has an unknown amount of kids. I think this explains why there’s so many Black Velaryons - there’s just like, a shitton of Velaryon cousins right now!

So once I established Corlys and his brothers as being mostly Summer Island descent, from there I moved onto who is likely a descendant of the Dragon Twins (and Corlys). For Rhaena’s many daughters, I thought of Targaryen names that sounded Andal-ish/Reacher-ish and Andal names that sounded Targaryen-ish; there's a pattern in the Reach of using the more religious-affiliated Targaryen names as Reacher names (Aemon, Aegon, and Baelor have all come up!) so I think at least part of this is Rhaena's influence. I decided on Alyssa, Leyla, Victaria, Aelora, Denyse, and Rhaella.

I also combined this with my “Elaena marries Baela’s grandson” theory, which I feel makes a lot of sense - not only the Penrose-Valyrian connection and story implications, but notably the name “Laena” is a Velaryon name. I think if Ronnel’s mother was also a Laena, and both of them were half Velaryon, this little bond between them of choosing a Velaryon name for their first born daughter feels very sweet and romantic even. PLUS, if a Targaryen descended girl marries into another house, I can see people wanting to show that off every once in a while through a name. This is why Rhaena’s girls marry a Costayne and a Hightower!

Then I started thinking about the timeline and what was happening politically as all these descendants of Corlys start marrying. Given that the Tarlys were staunch supporters of Rhaenyra, I can see Rhaena wanting to reward that, and Garmund agreeing due to them being a powerful Reacher house. Since there is mention of the Blackfyre Rebellion ~pitting brother against brother~ and the Costaynes sided with Daemon, I thought having a Hightower-Targaryen involved in that mess would be thematically fun; either Aelora sides against her husband or Aelora marries a Costayne that sides against the main branch. Either way, when the rebellion is over, Daeron punishes the main branch Costaynes by taking most of their lands and giving it to Aelora and her daughters. As for Denyse, I thought it would make sense, once again, for her to turn back to the Braavosi Sumer Islanders for a husband; a First Sword of Braavos, perhaps, who use Hightower grey and a pink dragon to represent Denyse's heritage in their sigil.