He is so cute!
Has he been to the vet yet? If not, you should really be keeping them separated until you can rule out feline leukemia, feline aids, FIP, distemper, feline parvo, rabies, and any number of other diseases strays can carry. Even if Jinx is indoor-only and up to date on vaccines (which I hope is true!), vaccines aren't 100% effective and it's better to be safe than sorry.
What are you going to name the orange kitty though?!