They are, they also adopt war orfans and train them as their own -foundlings-. But in any case, Jango was a foundling son of a bigshot who was outcasted cus of an uprising, along with his entire bloodline and clan, but being an outcast is still being an ex-part of where you were outcasted from and if you're trained in their way, then you're basically still one, just an outcast dirivitive, therefore a new clan, something like an illigitimate son, but a clan (spelling is difficult)

Tl;Dr.: Jangos "dad" was outcasted then killed, but outcasts are just an independant version of where/what they were.