We found a stray kitten with a very bad eye infection today. The vet says its about five weeks old. We have two indoor cats about four years old who were raised together. Can this kitten co-exist with the other two? They are generally ignoring it but hiss at it whenever they walk close to it. We have closed the kitten in a bathroom with an open cat carrier for the night. Should that work OK? Does a kitten know how to use a litter box instinctively or do we have to teach it to use one? The vet says wet cat food should be OK, but should we give the kitten that powdered cat milk sold at pet stores? Any other suggestions for us amateurs trying to do the right thing?