My daughter's friend has 3 cats of his own and our 6 year old neutered male hisses and "moans" when he sees this friend. The friend has been gentle, tries to pet the cat, and has done nothing to scare or tease the cat. What can we do? I'm assuming it's because the friend has his own cats and our cat just smells them. I'm afraid our cat might get aggressive toward this kid. Any suggestions?