Kesh is offering his holdings as free trade centers, which augments the efforts of the FREE LANDS OF THE TUNDRA. Which I appreciate, thank you Kesh.
But he is not (as far as I can tell) asking to JOIN the FREE LANDS group and therefore FCC would not be in the defensive pact (although it is their prerogative whether to get involved in any conflicts anywhere on the map - just like its Hospitaller's prerogative to do the same)