Hi Sandi,
Another bird in its own cage should be fine. And possibly the birds will choose to interact with each other. I have known many Timneh & Congo Greys who got along. One thing to keep in mind is these birds are capable of breeding with each other and producing hybrid offspring. Most aviculturists discourage this because it is better to keep the species pure. Even if the birds do not get along, most parrot owners have more than one parrot. They learn to tolerate each other even if they don’t get along.
Happy Holidays!
Brenda