Let’s distinguish Dog Brothers (DB) and Dog Brothers Martial Arts (DBMA).
1) Dog Brothers are a company of stick fighters, aka “the band of sweaty, smelly, psychopaths with sticks”. These stick fighters meet and fight at their Gathering of the Pack. Everyone who is interested to fight is welcome, no matter from what martial art he/she comes from.
To become a Dog Brother one has to be admitted into the “Tribe”. To be accepted as a tribe member one has to fight at Gatherings. The first level is “Dog”, this can be achieved after participating in several Gatherings. If the Council of Elders think the fighter has what it takes, the odds are that he/she ascend to “Full Dog Brother”, and gets his/her personal nickname.
2) DBMA however is a martial arts style founded by “Crafty Dog”. The influence of various martial arts and the experience in RCSF fights, led to originate this system of many styles. More about DBMA → here
It’s possible to train and learn DBMA without fighting at Gatherings. On the other hand it is not necessary to train DBMA in order to fight at a Gathering.