This isn't a particularly important part of Dawntrail, but it is one that I noticed and internally earmarked as something we aren't clearly told, I think it'd be good to have a place for us to try to get this as straight as we can:
How old is each claimant for the throne of Tulliyolal?
We're probably going to get this information eventually, but it's unlikely to turn up anytime soon; that's Encyclopedia Eorzea territory. Still, I think it's something we can piece some statistics together for, and I'd appreciate if anyone else can figure out anything more tangible than I can.
Wuk Lamat: This one's as concrete as we get; Wuk Lamat is somewhere in her early twenties, I would say twenty-three at the oldest. Hunmu Rruk's story about his daughter places the events that led to her adoption at around twenty years ago, and Wuk Lamat does say she's too young to remember. This would also track with her being childhood friends with Erenville, who's twenty-four.
Koana: His age only exists in vague reference to other events; he actually does remember the day Wuk Lamat was adopted, and by his own testament sounded mature enough to have protective feelings at that age... but Koana's also the type to overstate his maturity and rationality, so it's entirely possible he was just, like, five years old. Alisaie saw him in the Studium when they were both studying, but not close enough for them to cross over; Alisaie was admitted to the Studium at a young age, so her age range isn't useful, but Krile was a contemporary of the twins, and she's 22. My best guess is Koana's a few years older than Wuk Lamat; at the oldest maybe twenty-six. We don't know how long a Studium degree takes, but that'd give the right range for Alisaie to have seen him around, but not enough to actually know the guy.
Zoraal Ja: Nobody really talks about Zoraal Ja's upbringing, so we don't have relative references here, save that him being the 'First Promise' suggests that he was born before Koana was adopted. Weirdly, the main reference point I've got is his temperament; that's not a young man's childish scrappiness, but it's also not a weathered general's experience and determinism. A couple things compare him to Sephiroth, who probably gives us a workable age range: Zoraal Ja's probably in his late twenties. (At least, during the claimant challenge.)
Bakool Ja Ja: Alright, here's the rough one: to my knowledge, we have literally no clues on Bakool Ja Ja's age, or even relative life experiences and landmarks. We know his dad's the Autarch of Mamook, so he's probably kind of old, and I can't imagine he held off on trying to become a parent given the status symbols blessed siblings are, which would probably put Bakool on the older end of the claimants... but given what we know about blessed siblings, they probably didn't get it right the first time. Bakool's lament about other blessed siblings works either way, in different ways; either he's lived long enough to see a lot of other couples try, or he's been made aware that his parents tried a lot before him. I feel like Bakool's either the youngest or oldest claimant, nowhere in between, more by dramatic logic than material.
This is a completely irrelevant 'mystery', it literally does not matter, but it's one that's been sticking in my mind for a bit as a 'huh, now that you mention it' kind of question.