I have 2 neutered male cats (4 months and 6 months) who are super sweet and loving with me, but whenever anyone comes over, they hide under the couch. I'll have friends stay with me for a weekend and they will stay under the couch the entire time except to eat and use the litterbox. This past weekend, my sister and her boyfriend stayed for the weekend and the second they left, the cats jumped in bed with me to cuddle even though I hadn't seen them the entire weekend! They are so friendly and outgoing with me, but so miserable whenever anyone else comes over. I know it's probably because they're only used to being around me, but shouldn't they atleast be interested in meeting people if they've been in the apartment for 3 days? I don't want them to have any problems in the future if I ever start living with another human. Any ideas?