This relationship is almost exactly the same as Sasuke and Itachi in Naruto...
Fact 1: One of the brothers is an absolute genius
Fact 2: The father always gives the weaker one a hard time, but secretly thinks highly of them
Fact 3: The loser brother (yes Sasuke fanboys, he is a sore loser and you know it >=3) discovers demonic powers
Fact 4: One of the brothers kills the family (it's opposite, for 666Satan it's the loser, for Naruto it's the genius)
It's uncanny XD