The People app uses an intelligent merge feature to combine contact info from various sources (GmailTM, Microsoft® Exchange, Facebook®, new entries, etc.). If contact info was joined in error it can be separated back into individual contacts.
From a Home screen, tap Apps (located at the bottom).
If necessary, from the Apps menu (located toward the left) tap Custom.
Tap the appropriate contact.
Tap the Menu icon (located in the upper-right).
From the Suggest Link section, tap the Link or Unlink icon of the preferred contact, as appropriate.
If the preferred contact doesn't appear under Suggest links, tap Other contacts.