There’s nothing like watching the warm cuddly embrace of two cats licking and grooming one another. This behavior is called allogrooming and is usually occurs between cats that are related but can also happen between any cats that get along well.
Must studies have found that it is focused on the head and neck region and may also explain why cats enjoy being petted in those areas (and often pushing their heads into humans hands). Interestingly, one study found that higher ranking animals more often groomed lower ranking ones and that allogrooming may be a way to redirect aggression and induce a calming behavior.