They seem like they’re getting along already.
Have they tried going into each other’s areas? Or have you tried putting them in a small space together to see how they behave when they’re forced to be around each other.
I have an unaltered female and a brother/sister altered pair. They get along well enough though there is a bit of aggression from the altered female (Leia). It’s more territorial and my unaltered female (Pom) is so submissive that it never turns into a fight. That said, it’s only been recently that Leia will allow Pom into her hutch.
I should caveat that by saying, I never put any real effort into bonding them as I was trying to wait until Pom was desexed. I would imagine that with the dynamic you’ve described, it shouldn’t be too difficult. Just do it slowly and watch them carefully until you’re certain they’re not fighting.
However, if you’re planning on desexing your male, it’s best to wait until after he’s recovered from the surgery before you begin the bonding process.