Best to have both neutered I reckon. From what I've read on here, the unneutered male will be more aggressive, territorial etc. The best combo seems to be neutered male and speyed female from the comments I have seen on rabbit forums.
I would say it's not impossible as it will depend on the individual rabbits, but I guess it might be a harder bonding than if they were both neutered and a more volatile combination. Having said that, we have two neutered males who were bonded and fell out and they are proving difficult to reunite, so not even 'done' ones are not that easy to bond.
I am guessing you have a neutered male and have found an uneutered one you would like to have as a friend?