Tried switching and it appeared to work for all other leaders around Norway/Sweden.

For the others, it was defaulting to the character. Could change and then change back.

Do you have Prisoners of War active and turned on? I'll test in now.

I've had it active and was getting the same. Disabled the options and got the same.
Will try with it deactivated.

Because he's 17...and has a spiritual ethos...I can take a look at that and maybe tweak it a bit...so the Norse get more benefit.

OR = {
age >= 20 #Fine with not making knights be older as there are historical examples of people being knighted at 16 (though very rare) but less so for the person actually leading the army
AND = { #They're the king!
is_adult = yes
highest_held_title_tier >= tier_kingdom
}
AND = { #They're a leader of warrior people
is_adult = yes
culture = { has_cultural_pillar = ethos_bellicose }
highest_held_title_tier >= tier_duchy
}
AND = { #They can be a leader or our people
is_adult = yes
culture = { has_cultural_pillar = ethos_bellicose }
highest_held_title_tier >= tier_county
OR = {
martial >= high_skill_rating
prowess >= high_skill_rating
}
learning >= decent_skill_rating
}
AND = { #The Child Warrior Leader
age >= 12
culture = { has_cultural_pillar = ethos_bellicose }
highest_held_title_tier >= tier_county
martial >= high_skill_rating
prowess >= high_skill_rating
learning >= decent_skill_rating
}
}

Great. Thanks for pinning it down.