Need advice – 3 bunnies, one not neutered

(Reposting because I accidentally deleted this 😭)

I have a very unusual dilemma.
TL;DR – one of my 3 bonded bunnies turned out to be not neutered and I don’t know how to proceed with their relationship/what to expect post neuter.

Full context: about a month ago I went to a rescue to get my bunny Mimi (F, 3yo, black and white) a new friend after her bonded pair passed from GI stasis. Fritz, a 1yo male bunny (brown and white) immediately fell in love with her (instant grooming and chinning), so we chose him – but I later found out he has a brother Siggy (1 yo, white). They were dumped together and although they got along great the rescue decided to separate them because they’d have a better chance of getting adopted out separately than as a pair. Long story short I decided to try bonding all three of them to keep the brothers together – and they got along amazingly, so I now had three bunnies.

When I brought them home, however, I noticed that Fritz seemed to have a single testicle on his left side. In the next few weeks he exhibited all the behaviors of an un-fixed bunny – spraying, humping, grunting, poo everywhere, and him being very stinky. The rescue told me both brothers were neutered a month back, so any hormonal behavior should have already died down. To be clear, I do not blame the rescue for this at all – I know the person who runs it well and trust her completely. I fully believe she was misinformed by the vet. In any case, I was convinced he wasn’t fully neutered and confirmed as much with my vet last week. Furthermore, I obtained his medical documents from the rescue – apparently the rescue’s vet could not find his testicles at all, so the procedure was labeled “neuter successful – patient already neutered”. I’m baffled as to how this is possible as he very clearly has one testicle but it’s what it is.

I have him scheduled for a neuter with my vet on Wednesday – but I’m at a loss what to do after. This is such a bizarre situation. I know male bunnies need about 6 weeks for the hormones to fully leave their body – but do I absolutely need to separate Fritz from Mimi and Siggy during this time? There has not been a single fight in the month and change he’s been here – Mimi won’t let him mount her and he lets his frustration out on Siggy, who does not object, which seems to appease Fritz for a short time. Outside of him wanting to mount her and her grunting and shaking her tail at him/running away, I’ve witnessed no other frustration – the exact opposite in fact. Frequent groomies, cuddling, and always spending time together. Clearly they all love each other so the idea of separating them is devastating to me.

Is there any world where I can keep Fritz with Siggy and Mimi after his neuter? Is there a chance their bond won’t break because his hormones will be changing? I could really use some advice here 😭

by chachachingus