Sibling rivalry is one of the oldest dated conflicts in the world with the first murder ever to be recorded as a result of it. From the very beginning, the relationship between these half brothers was never going to be a good one. It was doomed from the start.
They were born from two different women with the only common denominator being their father. The deep hatred and disdain was passed down directly from that umbilical cord when they were born and their father didn't help matters favouring one son over the other. All this was in the outside world but the feelings ran so deep that Qie Ranzhe reflected their terrible relationship in-game.