Dog chews the fur of its companion and vomits it later

There's a liquid called "bitter apple" which is an extract of naturally astringent apples. It does nothing more than taste bad. With a lot of luck you can get it in a drug store, otherwise ask in a pharmacy.

Rub a few drops of the extract on the spots Harley is chewing on.

Even better: ask your vet for a skin ointment for Tubby. Skin that is being excessively licked is often dry and itchy. The ointment should help the skin regenerating and the fur growing back. First rub the ointment on Tubby, then add a drop of bitter apple on top. One (fresh) raw egg fed every second or third day is a natural food supplement to improve fur quality as well.

Then you need to treat the reason why Harley chews on his father. If you just make chewing on Harley unpleasant, but don't treat the actual cause, he will soon develop a substitute behavior (that you probably won't like as well). My guess is that he's either bored or very anxious. We have compiled a list of different activities to entertain bored dogs in this question.