Feline hair-loss is actually quite common, however patchy fur usually signifies some sort of problem with your cat.
If a cat loses large amounts of fur in a particular area, you should normally be able to notice broken hair shafts. If this is the case, then the hair is not falling out, but rather being taken out. This is almost always down to the cat continually licking an area; the tongue gradually breaking down and removing the hair. It is then best practice in most circumstances for treatments to focus on the reduction of licking. This does require close attention to determine the initial cause of licking, and in doubt a visit to your vet would be recommended.
One of the causes of licking can be irritation to the skin. An obvious cause would be fleas, ticks, lice or mites. Obviously there’s a variety of treatments to tackle this (i.e. Coatex). Other common irritations would be allergies, for instance air-born allergens or even if you have recently changed cat food.
75% of cats suffer from arthritis. A cat will lick the area of that joint to relieve the pain, in the same way people massage their sore muscles. It would always be recommended for you to provide the appropriate pet meds, especially for your older cats who would be more prone to arthritis. Dorwest Herbs would be a fine example of a cod-liver oil for cats, which keeps joints supple.
If repetitive licking is not down to some sort of pain relief, then your cat could be diagnosed as having an obsessive compulsive disorder (OCD) best known as psychogenic alopecia; a main causal factor being stress. Repetitive self grooming is a way they find of relieving this stress.
There are stress relieving treatments available, Feliway being among the most popular. However, you might find that the best respite for stress is attention and play. The main cause of stress for cats is, in fact, other cats. You may find that by providing more cat toys means that your moggies don’t have to share, therefore having to interact less with each other.
Whatever the issue may be, a visit to the vet would always be recommended. Ultimately, we all want stress free, fully furred cats. The better the environment, and the more attention for your cats, the less likely they are to suffer from hair loss. As long as you think along those lines, you shouldn’t come into any serious issues.