Tarinya’s answer to “OK, now I feel silly that I have to ask this question, but who is older, Kaden or Valyn? I had alwa…” > Likes and Comments

Kaden is older, but his eyes, not his age, are why he inherited the throne.

"'There’s nothing to know!' Adare had complained. She was eight years old at the time, which meant Kaden was five and Valyn even younger. 'They’re babies. They play like babies and they cry like babies.'"

Staveley, Brian. The Providence of Fire (Chronicle of the Unhewn Throne Book 2) (p. 137). Tom Doherty Associates. Kindle Edition.