My Arcanine and Houndoom can't get along. They're both males, I raised them both from pups, and they're both total sweethearts individually, but they constantly bark and growl at each other and fight whenever they can. Is this normal? Have I raised them wrong?
I doubt it.
The part about raising social Pokémon is that…well…they fight. Wild Pokémon fight, tame Pokémon fight, herd animals fight, pack animals fight. Heck, even people fight. Whenever you get more than two individuals together, there is always a chance that they will not get along. Fighting Pokémon do not necessarily mean you have done something wrong or bad. Sometimes it’s just instinct/personality/bad luck.
So do not feel guilty about it. Do, however, get help.
Unfortunately, I am ill-prepared to suggest Pokémon training tips, particularly for social interaction, but your local Pokémon Center should have contact information for trainers, training clubs, classes, and Pokémon psychologists. They will be able to guide you through this.