WAHAHAHAHA! Even the extras confirm it!
Early in the commentary for Deconstruction, JMS stated that after they shot the Londo & G'Kar mini-scene, one of the extras actually asked him how long they (Londo & G'Kar) had been married. Also amusing was JMS's follow-up thought immediately thereafter in which he described G'Kar as the long suffering wife listening to her husband (i.e., Londo) prattle on and on.
G'Kar, of course, will be lodging an official protest for being cast as the wife. *eg* But yay! Acknowledgement of deliberate subtext from the Great Maker himself!