While membership in most Dragaeran Houses is hereditary, especially among the Lyorn, there are at least three known exceptions to this.
Dzur[]
This house is one of the few that allows outsiders to join, provided that they can defeat 17 Dzur Heroes hand-picked by the leaders of the House. Needless to say, this has hardly ever happened in the recorded history of the Dzur. (Although we know that Mellar did it, the Dzur were careful not to let anyone else know about this.)
Jhereg[]
Unlike the other houses, being a Jhereg is not necessarily a hereditary condition. Titles are sold by the Jhereg Council to anyone who can afford the expense. This includes Easterners, Teckla, and members of other houses (such as Kragar). Jhereg will even sell titles to crossbreeds. Mellar is an example of this.
Teckla[]
Anyone can be a Teckla, even Easterners. Typically a Teckla is bound to a patch of land (since most Teckla are farmers) in the Feudal tradition of Dragaera. Teckla are not nobles so this is not a particularly attractive prospect, even for Easterners. Teckla are, however, still Imperial citizens, and thus have a link to the Orb, and theoretically are allowed to practice Sorcery--although few Teckla have the education necessary to actually do this. (Paresh is one example of someone who overcame this. Miklós also learned sorcery as a Teckla, though he had had a prince's education previously.)
- See also Speculation:Joining_Houses.