I don't know who Talia al Ghul is, but if she does appear, I think it would be a little incongruent for her to be Arabic
Not if her mom is.
True. But if her mom is Arabic, why does Dad have an Arabic name? Is there a connection or is it just a coincidence?
I believe that Ra's Al Ghul was born in the middle east in about the 8th century AD... prior to the rise of Islam but instead during the time of the greatest cultural success in the region. During that period, what we now call the Middle East was a thriving, bustling region... really the center of the world, with trade from Africa, the west, and the east all going through there.
My point? It wouldn't be all that surprising for someone from Asia or Europe to have settled in that part of the world at that time. The fact that after the fairly bloody rise of Islam throughout that region, most of those people had either fled or been killed, doesn't negate the fact that there were people from throughout the "civilized" world living there at the time.
Now, the guy's actual name need not be Arabic... because I'm sure that nobody would actually name their child "Head of the Demon" (which is what Ra's Al Ghul" means) He took the name and forgot his original name... and since he's only been called Ra's for many centuries now, that is, effectively, his "real" name now.
He led an organization created in the middle east which became a "shadow" organization when it was driven underground during the rise of Islam, and which acts exactly as described in the film... as an agent of "justice" in the world (as seen by its members and its leader).
When Denny O'Neil created the character, he made him Arab, but realize that this was before the "politically overcompensation" we have today where we can never talk about any Arab people (which is, by the way, not the same thing as Muslim people necessarily!) in any negative way whatsoever. Movies made from Clancy novels must substitute "white supremacists" for Arabs because it's not acceptable to have Arab villains, ever, now...
Which is every bit as racist as saying that every Arab is a villain, when you stop and think about it, isn't it?
This, I'm sure, was central to making Ra's either a far-eastern asian or a Frenchman (with an english accent) for the film. It doesn't matter... RA'S is still Arab. And thus, so is his daughter. No matter what the nationality of the actors playing them happens to be.