How do multiple chinchillas bond

My family may or may not be getting a second chinchilla. If we do then I wanted to know how they would bond. Ours currently is about 11 years old and the new one, we don't know yet. But probably a similar age. Also how big would there cage need to be. this is the cage we have now, with more platforms and a spinning wheel, is this big enough?

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How do multiple chinchillas bond