Per this dev post, at least for miqo'te, cross-breeding between clans can happen. It mentions that a particular NPC may have had some blood of the other clan in her past (among other possible explanations), which explains why she has Keeper features and a Seeker name. It seems the only barriers to cross-clan breeding are social and distance-related.
The Freelance Wizard
Quality RP at low, low prices!
((about me | about L'yhta Mahre | L'yhta's desk | about Mysterium, the Ivory Tower: a heavy RP society of mages))
Quality RP at low, low prices!
((about me | about L'yhta Mahre | L'yhta's desk | about Mysterium, the Ivory Tower: a heavy RP society of mages))