I do believe this has already been confirmed in lore and through dev statements that all the Eorzean races and their sub-clans/tribes/whatever you wish to call them can inter-breed (actually, I know, as this inquiry has come up before ^^;; I just don't have the material on hand).
EDIT
All found from HERE.
EDIT
(03-05-2015, 07:08 PM)Unnamed Mercenary Wrote: SE Confirmed that mixed races exist.
All of the playable races have a common ancestor. (Stated at the Las Vegas Fanfest)
However, they are exceedingly rare and we do not know what they would look like.
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As far as interbreeding between different clans of a given race, it happens. Chances are, there would be mixed physical traits from each. (Maybe the Keeper fangs and the Seeker eyes?)
As far as cross-clan miqo'te go, the naming conventions actually talk about it directly.
http://finalfantasy.wikia.com/wiki/Miqo%27te/Naming
(03-05-2015, 07:30 PM)Xenedra Wrote: Here's our old buddy the lore forum with our favorite guy, Fernhalwes ♥.
See question number 2:
http://forum.square-enix.com/ffxiv/threa...post490835
(03-05-2015, 07:40 PM)Tiergan Wrote: F'lhaminn is actually a Fernhawles-confirmed half-breed miqo'te. Â She has a Sun Seeker name and was brought up as a Sun Seeker, but has obvious Moon Keeper traits (most obvious being the rounded pupils).
I'm really, really curious what a Hellsguard/Sea Wolf combo would look like because they're the only race where the skin-tones really don't have any point where they intersect.
(03-05-2015, 07:41 PM)K Wrote: Here are some links to a few past topics that brushed upon this subject in case you are interested ^^
Clan Mixing
Half Elves
Cross-species / Cross clans offspring
All found from HERE.