Do you think that being in a "group" means you need to be with people that booked into your "group" for the entire cruise? Well, that's not the case! If you've taken a few cruises, somewhere along the line, your agent has put you into a group, or you booked into group space off a site on the internet.
Groups can be folks who are related, friends, co-workers, or complete strangers. Being in a group means that you get lower rates and little "perks" for booking into the group. A good travel agent will look for a group to put you in so you can get lower rates and amenities. You won't know you're in a group, but you'll get the benefits of being in one!
So, the next time you make a reservation, ask about group rates. You just may benefit from being one of the gang!