can_marry_character_trigger

can_marry_character_trigger = {
	save_temporary_scope_as = can_marry_char_check
	OR = {
		AND = {
			is_betrothed = yes
			betrothed = $CHARACTER$
		}
		AND = {
			can_marry_trigger = yes
			$CHARACTER$ = { can_marry_trigger = yes }
		}
	}
	trigger_if = {
		limit = {
			$CHARACTER$ = { is_concubine = yes }
		}
		$CHARACTER$ = { is_concubine_of = scope:can_marry_char_check }
	}
	trigger_if = {
		limit = {
			is_concubine = yes
		}
		is_concubine_of = $CHARACTER$
		$CHARACTER$ = { could_marry_character_trigger = { CHARACTER = scope:can_marry_char_check } } #Gender, recent divorce, allowed to marry, no illegal incest etc.} If they're your concubine you're rules are the ones looked at
	}
	trigger_else = {
		could_marry_character_trigger = { CHARACTER = $CHARACTER$ } #Gender, recent divorce, allowed to marry, no illegal incest etc.
	}
}

As written in game/common/scripted_triggers/00_marriage_triggers.txt.