mpo_blood_brother_warrior_trigger

mpo_blood_brother_warrior_trigger = {
	can_be_combatant_based_on_gender_trigger = { ARMY_OWNER = $OTHER_BROTHER$ }
	OR = {
		prowess >= monumentally_high_skill_rating
		AND = {
			prowess >= extremely_high_skill_rating
			OR = {
				has_trait = lifestyle_blademaster
				has_trait = education_martial_prowess_3
				has_trait = education_martial_prowess_4
				AND = {
					has_trait = tourney_participant
					OR = {
						has_trait_xp = {
							trait = tourney_participant
							value >= 50
							track = foot
						}
						has_trait_xp = {
							trait = tourney_participant
							value >= 50
							track = horse
						}
						has_trait_xp = {
							trait = tourney_participant
							value >= 50
							track = bow
						}
					}
				}
				has_trait = berserker
				has_trait = sadistic
				has_trait = vengeful
				has_trait = brave
				has_trait = wrathful
				has_trait = aggressive_attacker
				has_trait = reaver
			}
		}
		martial >= extremely_high_skill_rating
		AND = {
			OR = {
				prowess >= very_high_skill_rating
				has_trait = education_martial
				has_lifestyle = martial_lifestyle
			}
			dread >= 60
		}
	}
}

As written in game/common/scripted_triggers/mpo_scripted_triggers.txt.