Omega = orphan who was abandoned in a snowy night, was found by his new father (he only adopted him because he was a omega). Has a family complex, wasn't loved just used as a tool and his father always cursed him for being useless (he has a condition on his pheromones). He was basically sold to marriage with a son of a conglomerate (Kwon Ido)
Alpha= unknown past, knows the omega (Sejin) too well even before they met officially, seems to know Sejin from his childhood (or another life because he left intended that they fucked before Sejin's second heat)
Beyond Memories