At least in my experience, mandarins don't really pair with each other, but a lot of fish don't mind them being around so they'll hang out together.
My male mandarin and orange spot goby for a year or more kept having deep conversations... I would walk up to the tank and they would just be like an inch apart, facing towards a spot a little in front of them, like they were buddies chatting around a fire. I think it stopped when the lawnmower blenny was added, because while he wasn't aggressive, the orange spot goby really didn't like when he was close - fins out, mouth open, sometimes moving its head a little off the ground, then running off when the blenny just kept munching and swam on by.