None of them really have a secret talent, but they're kind of special as far as social classes go. Celeste is one of the princesses, and in better shape than the king to go to the relics' shrines, Liam is the son of the former head of the military, Alice isn't part of the main story that much, and Conall is a homeless thief. Celeste would naturally want to be a part of her sister's rescuing team because she really doesn't want to lose more of her family. She's also that young so she is more open-minded and still hasn't fully formed her thoughts about the world, which is crucial for what I'm planning for the story. Liam is primarily her best friend, and I don't want their ages to differ too much so they can stay around the same level of maturity. Liam was also raised, somewhat ineffectively, by his father to become a knight. His bodyguard position was given to make him feel important, but also to see if he likes the idea and is good at it.
Alice and Stefan, on the other hand, I might make a bit older, but I want the age gap between Alice and Celeste to be small enough that they can relate to each other really well and that Alice doesn't feel the need to baby Celeste as much. Stefan was somewhat of an out-of-the-blue character, though, so I guess I can make him older.
Conall's age protects him from the wrath of Celeste and her guards, and invokes pity in Celeste because she lost her mother around the same age as him. He sets out on his quest with an idealistic and naive goal, to journey across the continent to assassinate the king all by himself, and it's stupid to the point that no adult would do something like that. He also doesn't really fight in battles so much as steal things and pick locks.
Also, I guess I should've put this here already, but there's a time skip of about 8-10 years halfway through the game. And sorry if this post is intimidatingly long, but I didn't intend to type out this much.