Genetics matter and inbreeding does have an impact on genetics. With Ball Pythons inbreeding one generation is not 'critical' but it is one step towards a slippery slope.
If you have a sibling pair you are keeping as pets, if they do breed and you want to try your hand at rearing the eggs, have fun with it...
But if you wish to breed as a hobby, then I suggest making the investment of an unrelated mate for your snake/snakes.
It should not be believed that new morphs are created through inbreeding. A couple have been discovered by wild caught siblings, but that is because each snake was het (heterogenous) for the morph it created, not because they are siblings.
