When we got our second cat, Gabriel, he was a tiny kteitn, only about 2 1/2 months old. We kept him separate for about 2 weeks, just letting my other cat, Salem (he was a year old) see him a few minutes at a time. When we finally released Gabriel to the rest of the house, Salem was pretty much used to him and ignored him for awhile. Once Gabriel was about 6 months old though, it was on! But Salem was surprisingly gentle with him, for all his rough and tumble ways. I guess it depends on the cats and their personalities really. Since Bailey is so easy going, he may surprise you.