How can I get a GameCenter friend's real name instead of their alias/nickname?

I'm trying to make a leaderboard in my iOS game, similar to the one seen on the results screen in Jetpack Joyride. I want to display a list of scores of the user's GameCenter friends, but I want to see their real names on the list, not their nicknames (so John Doe instead of GenericUser456, for example). Right now I have a list of friends and scores being returned, but the IUserProfile class doesn't have any field indicating their real name; the userName field just returns their nickname. Is there a way to get the user's real name in Unity at all without a plugin, or will I need to find something else to accomplish this?

Thanks in advance! :)