I don't know, but with my greys, I let them both keep their "own" cage and built a little tunnel/passageway between their two cages and connected them. That way they both get to keep their own space yet be together if they feel like it. It's been that way for several years. I'm sure they could share one cage now, if they felt like it, but I just keep it the way it is because it's part of their little territory and too much trouble to move one cage out of the house LOL.
If you can spare the space, it's like a double-size condo
Joanne