pam-- i'm guessing neither cat owner is in a position to reclaim their cat? if the owners haven't left recently, i would then suspect health problems. usually, wetting behavior indicates a medical problem. a cat who is missing their owner might wet also, but if the owners have left them before and the wetting is a new problem, then look more towards medical reasons. male cats in particular are prone to urinary tract infections, especially if they were neutered too young. ask the cat owners what they expect you to do, and remember, the cats are their responsibility before yours.
good luck, it is hard when you are allergic to deal with someone else's problem. i love cats, have 2, and think you might re-home them through a rescue group-- a local one rather than spca or humane society. our humane society chapter puts animals down for ear mites, so i no longer recommend them, and smaller rescues often take animals who's time is up at the spca.