A friend of mine recently confided that her two cats Lupin (he's on top) and Swarley co-exist without much rivalry, but they occasionally break out in fights for no apparent reason. In fact, Lupin has a fat lip in this photo from fighting with Swarley. It's generally understood that competition between felines in multi-cat households is common (and even unavoidable). The Humane Society of the United States goes so far as to say:
If the battles between your feline family members are anything like the struggle between Cain and Abel, there are a few things you can do to prevent the "sibling rivalry" from reaching biblical proportions. Of course, it's almost impossible to guess how well any particular pair or group of cats will ultimately tolerate each other; some unusually territorial cats may never adjust to sharing their house, and may do best in a one-cat family.
Do your furry friends get along or do they have a sibling rivalry?