[ Fortunately, Gregor really doesn't know Bel well enough to predict how they would react, and he's consequently prepared for anything. He'd slipped into social-duties-mode at some point in the last several seconds, and for all he can't tell how much water is under the bridge between Miles and his subordinate, he can read Miles's feelings on the matter clear enough over the link as to be confident in his position.

That's really all he needs to field this like he fields every other jibe meant to get under his skin. This is a new version, but it's the same old dance. And, too, he doesn't want Miles to wonder about his reaction or how he'll take it; he feels perversely protective of their relationship, at this first real confrontation to it, rather than the pithy comments of his mother and Captain Illyan. If anything, they'd just set him up to be out of patience for others critiquing their private lives, where they have no say. ]

We have a third, actually, [ he says smoothly, and pulls on every lecture he's ever had from Cordelia to add, ] The consenting process for adding to our arrangement is fairly complicated. Certainly something I would recommend taking longer with, and in a more private space, than we have available here.

[ Said with the absolute blandest demeanor he can pull off, which is bland indeed. ]