That's the entire point. Dog Brother #1 is the champion of the lost and disenfranchised and as such, can not be groomed. If he had been groomed and prepared for this role, he would not be one of the lost souls of this world anymore, he'd be one of the privileged and could not be their brother. Fate has dealt these orphans and strays a rough hand, but if just about anyone can become their champion, that also means just about anyone can escape their harsh fate. It's not so much about who he is, but about what he repesents. A glimmer of hope for everyone who's hit on hard times, who's been down on his luck. After all, if some random street urchin can become one of the greatest fighters that has ever lived, so can you. That's why Dog Brother #1 is the only one of the Immortal Weapons that never fights alone. He has an entire army to back him up. If not in flesh, then at least in spirit.