BenzMama is correct, you have to maintain the proper pecking order meaning the first bird there stays first in everything, first fed, first spoken to, first to be let out and so forth, that will keep the first one's nose from getting out of joint, so to speak. Maintain supervision when they are out at the same time to make sure no conflicts take place, maybe you will be one of the lucky ones and they will tolerate each other but there is no guarantee that they will. We have many members who have more than one grey and they do just fine.