eren is alpha, levi is omega. eren is a child when levi meets him and he tries to ignore his mating instincts until he goes into heat and is assaulted by another alpha. eren intervenes but levi kicks him out to get him away from him before he does something that he would regret. parents find out and they separate them until erens high school graduation. no sex is shown but implied.
Shingeki no Kyojin dj - Ore no Alpha