Im not too sure about mice but I can give you my opinion, correct me if im wrong anyone!
When you take a male out I think he would be cranky. Hes probably just a little unaccustomed to the new smell of his new cage and he is prolly a little ticked he cant be with his mate too.
Ive known situations where 1 male mice/rats has neutered and he is able to be in the cage with any other mouse/rat regardless if they are altered or not because he is much calmer and less hormonal to be with. I think its roughly what the mouses personality is like and what he will allow in his territory.
If he could be neutered and placed with females, he would be very happy!
Regardless of the circumstances or if they knew each other before, its important to do slow introductions all over again. This will let you know if either of them is aggressive towards one another and if they will become a close family again.
With my hamster pups, I do re-introductions with their Dad since they nearing adulthood and will soon live with him. He knows they are his pups but there is always the case where he rejects or finds them offensive.
Really, I think its all about smell.