Thanks for the responses, guys!
Unfortunately, I can’t place their cages opposite each other, as I have a double-level bunny condo (ramp blocked off while they need to be separated). My vet (an exotics expert who has performed many rabbit alterations) feels comfortable performing the spay as young as four months, provided my girl gets up to a pound of body weight, so we’ve just got a month left to get through. I have an xpen clipped to the front of the condo, and when she’s out in the pen by herself she makes a point of going up to the lower cage where her brother lives and sniffing with him. I do let them have a little time together when I can sit in the pen with them and keep my eyes totally on them (the vet feels this is safe, provided I’m always watching), but it’s not a lot of time. Still, they seem to continue to be OK with each other; in fact, just a day or so ago they flopped down side-by-side and chilled for a quarter of an hour.
When my boy is having his solo pen time, I’ve been introducing him to veggies, which he loves. I’m trying to bond better by making him take the romaine from my hand. He will sit up close to me for that, and let me stroke his head/back, but it’s very clear that he’s enduring it rather than reveling in the pets. *sigh*