likely_to_commit_incest_with_trigger

likely_to_commit_incest_with_trigger = {
	$CHARACTER_1$ = {
		OR = {
			NOT = { relation_with_character_is_incestuous_in_my_rite_trigger = { CHARACTER = $CHARACTER_2$ } }
			AND = {
				sexually_liberal_trigger = yes
				OR = {
					# Doesn't care much about social taboo
					has_trait = callous
					has_trait = cynical
					has_trait = eccentric
					# Lack of contact with other members of their attracted sex
					has_trait = reclusive
					has_trait = shy
					# They think they can get away with it
					has_trait = deceitful
				}
			}
			# A bit of a weirdo
			is_deviant_trigger = yes
			# I've incested before, I will incest again!
			is_incestuous_trigger = yes
			# Shared trauma
			AND = {
				any_relation = {
					type = rival
					has_relation_rival = $CHARACTER_2$
				}
				stress_level >= 1
			}
			$CHARACTER_2$ = {
				is_ai = no
				has_perk = subtle_desire_perk
			}
		}
		save_temporary_scope_as = incest_evaluation
		NOT = { #under 20 trigger is a HARD limit
			guaranteed_under_20_incest_rejection_trigger = {
				TARGET = scope:incest_evaluation
				SEDUCER = $CHARACTER_2$
			}
		}
	}
	$CHARACTER_2$ = {
		OR = {
			NOT = { relation_with_character_is_incestuous_in_my_rite_trigger = { CHARACTER = $CHARACTER_1$ } }
			AND = {
				sexually_liberal_trigger = yes
				OR = {
					# Doesn't care much about social taboo
					has_trait = callous
					has_trait = cynical
					has_trait = eccentric
					# Lack of contact with other members of their attracted sex
					has_trait = reclusive
					has_trait = shy
					# Deceitful trigger not present here because CHARACTER_1 is assumed to be the instigator, CHARACTER_2 doesn't necessarily actively want this, so getting away with it wouldn't motivate them into doing it
				}
			}
			# A bit of a weirdo
			is_deviant_trigger = yes
			# I've incested before, I will incest again!
			is_incestuous_trigger = yes
			# Shared trauma
			AND = {
				any_relation = {
					type = rival
					has_relation_rival = $CHARACTER_1$
				}
				stress_level >= 1
			}
			$CHARACTER_1$ = {
				is_ai = no
				has_perk = subtle_desire_perk
			}
		}
		save_temporary_scope_as = incest_evaluation
		NOT = { #under 20 trigger is a HARD limit
			guaranteed_under_20_incest_rejection_trigger = {
				TARGET = scope:incest_evaluation
				SEDUCER = $CHARACTER_1$
			}
		}
	}
}

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