The red and white (Rusty) is 13 years old and Oscar is 9. They are either getting along great or snarling and snapping at each other. There doesn't seem to be much middle ground with them.
Mostly they are getting along great. In fact, if I take just Oscar out of the house (like to the vet), Rusty will howl the entire time that he is gone! I don't know if he misses him, or if he is jealous that he doesn't get to go along too.