make_blood_brother_save_common_enemy_effect

make_blood_brother_save_common_enemy_effect = {
	save_temporary_scope_as = blood_brother_temp
	#DUKES OR HIGHER
	#Nemeses and rivals
	if = {
		limit = {
			any_relation = {
				type = nemesis
				mpo_blood_brother_common_enemy_sub_trigger = yes
				mpo_ideal_common_foe_trigger = yes
			}
		}
		ordered_relation = {
			order_by = max_military_strength
			type = nemesis
			limit = {
				mpo_blood_brother_common_enemy_sub_trigger = yes
				mpo_ideal_common_foe_trigger = yes
			}
			save_scope_as = shared_foe
		}
	}
	else_if = {
		limit = {
			any_relation = {
				type = rival
				mpo_blood_brother_common_enemy_sub_trigger = yes
				mpo_ideal_common_foe_trigger = yes
			}
		}
		ordered_relation = {
			order_by = max_military_strength
			type = rival
			limit = {
				mpo_blood_brother_common_enemy_sub_trigger = yes
				mpo_ideal_common_foe_trigger = yes
			}
			save_scope_as = shared_foe
		}
	}
	#You have a house feud against someone recipient is also opposed to
	else_if = {
		limit = {
			exists = house.house_head
			exists = scope:recipient.house
			NOT = {
				house = scope:recipient.house
			}
			house = {
				any_house_relation = {
					has_house_relation_level = feud
					any_relation_house = {
						house_head = {
							mpo_blood_brother_common_enemy_sub_trigger = yes
							mpo_ideal_common_foe_trigger = yes
						}
					}
				}
			}
		}
		house = {
			random_house_relation = {
				limit = {
					has_house_relation_level = feud
					any_relation_house = {
						house_head = {
							mpo_blood_brother_common_enemy_sub_trigger = yes
							mpo_ideal_common_foe_trigger = yes
						}
					}
				}
				random_relation_house = {
					limit = {
						house_head = {
							mpo_blood_brother_common_enemy_sub_trigger = yes
							mpo_ideal_common_foe_trigger = yes
						}
					}
					house_head = { save_scope_as = shared_foe }
				}
			}
		}
	}
	#In faction against someone recipient is opposed to
	else_if = {
		limit = {
			liege ?= {
				any_targeting_faction = {
					any_faction_member = {
						this = scope:actor
					}
				}
				mpo_blood_brother_common_enemy_sub_trigger = yes
				mpo_ideal_common_foe_trigger = yes
			}
		}
		liege = {
			save_scope_as = shared_foe
		}
	}
	#You are at war with someone that recipient is also opposed to
	else_if = {
		limit = {
			any_war_enemy = {
				NOT = { has_variable = rebel_leader_peasants }
				any_character_war = {
					is_war_leader = prev
					is_war_leader = scope:actor
				}
				mpo_blood_brother_common_enemy_sub_trigger = yes
				mpo_ideal_common_foe_trigger = yes
			}
		}
		ordered_war_enemy = {
			order_by = max_military_strength
			limit = {
				NOT = { has_variable = rebel_leader_peasants }
				any_character_war = {
					is_war_leader = prev
					is_war_leader = scope:actor

As written in game/common/scripted_effects/09_dlc_mpo_scripted_effects.txt.