So let's talk about one of the heads of Limsa Lominsa's pirate gangs and one of the High Houses of Ishgard. Now I've harbored suspicions about Carvallain's past for some time with a loose trail of breadcrumbs left about. Carrilaut, a knight stationed at the Observatorium and in service to House Durendaire (as they guard said Observatorium) mentions that the heir House Durendaire was lost at sea, attacked by corsairs.
Carvallain himself mentions "if my family hadn't been murdered at sea, I'd have no doubt followed my fortune-telling father into a life of divination." Woah woah woah now, if you've done the Astrologian quests you know you pay a visit to Carvallain. He mentions his fortune-telling father and we know that's Sharlayan Astrology in a very boiled down form.
So right now, you're probably going "okay Rocl but what does this MEAN? I'm sure people die on the high seas of Hydaelyn all the time! Seems pretty circumstanial" Well, I always entertained that Carvallain might be the lost heir of Durendaire. His complaints of a "fortune-telling father" complicate that a bit as we know Ishgardians aren't very accepting of Sharlayan Astrology but it could be Ishgardian Astrology too though since the idea of an Ishgardian practicing Sharlayan Astrology undoubtedly would've come up with Jannequinard so far. (Speaking of which, Jannequinard is unusually dark for an Ishgardian elezen and Carvallain's hue is very similar as are their hair and eye colours)
Why didn't Jannequinard recognize him? Jannequinard isn't the most observant person (see Rufin-Levava) additionally Jannequinard was in Sharlayan when the Durendaire heir was lost at see (both events match up to roughly 20 years ago). So there's definitely probably some sort of timing there that can lead to a plausible handwave.
Now, the most damning evidence requires a little bit in the wayback machine:
The above text is referenced in ye olde 1.0 promotional materials from before launch. I'm sure something there should strike a chord within anyone who got to about Lv52 in the Heavensward Main Scenario. Gorgagne. Gorgagne Mills' Vista Record goes on to say "Ser Gorgagne was a proud knight and bannerman of House Durendaire, until the fateful day when the heir of that house vanished from his sight while under his care, never to be seen again."When choosing a weapon, there are those who would turn their noses up at the axe, believing it too brutish for their delicate sensibilities. Pah! I say to them, I've never known a cloven head to complain.
-Carvallain de Gorgagne, Captain of the Misery, and leader of the Kraken's Arms
We now have a more concrete tie between Carvallain and Ishgard. If he's not the Heir of Durendaire, he's certainly at the very least the son of a man sworn to them. Perhaps he picked up the name from his steward (as Ser Gorgane is said to hang up his blade so he might've not exactly been an astrologian, but that could be metaphorical) Strengthening this tie is that during the Culinarian quests we learn that Carvallain has a softspot for Ishgardian cuisine and considers the Chef of House Durendaire the foremost authority on it. Another breadcrumb for the trail, which admittedly doesn't lead to a direct conclusion but definitely brings us close.
The point is I haven't finished Culinarian or Astrologian quests yet, but all of this information I needed to put down somewhere and see if everyone thought I was as crazy as I feel.