An older brother who walks in on his younger, cuntboy brother getting off and decides to help? A cuntboy nephew hot for his uncle and decides to seduce him? A cuntboy freshman on the high school wrestling team who has teased one of his teammates for too long and finally gets what he wants in the locker room after practice (or from his coach)?
An omega stays behind in his dorm with his Alpha roommate for the holidays and goes into heat with only his roommate to fulfill his needs? An omega son goes into heat for the first time and the only one allowed to knot him into submission being his Alpha father?