There are reams to be written about what is or is not a civilization, or which group belong together, but I cannot agree with the idea that dynastic change should be held equivalent to civilization change, and I cannot agree that two states that have been separate, speaking separate languages for nearly a millenia at this point can reasonably be grouped as the same civ (whether both equally need to be in the game is a separate question).
I'm also a firm advocate that civilizations should represent the whole history of a group or people, rather than the notion of making civilization snapshot of a culture frozen as it was at a specific point in time. It is better for game design (as it makes the civilization less of a single-era pony), and better for historical accuracy, as most civilizations have experienced multiple golden ages at multiple points in history.