In the case of empires knowing each other:

As the Namilee never really had an empire and I assume their territory is somewhere around the border of X'cor space, I'm going to assume people might know OF them, and they might know OF other species, but they're relatively isolated historically (sans from a race they uplifted - which probably got eaten by the X'cor) and maybe exploring civilizations.

Basically, they might have met people, but as they were never expansionist... Well, they never expanded much.