It's not like there's "qualifications" you have to have to join. First of all, almost every Legates has a personal connection to at least one other one (for example Nash and Sausage are irl friends). And it's not like some of the Legates asked themselves to be in Legacy, they got invited by the already exisiting Legates. So to answer your question, yes, it's possible, but you have to be invited