From A Song of Ice and Fire : TMG Wiki

Units and/or Attachments that list CHARACTER on their Stat card are unique. Only 1 copy of each of these Units/Attachments may be included in your army (though you can have several different Characters in your army). Note that several Characters might have multiple versions (such as Jaime Lannister “Kingslayer” and Jaime Lannister “The Young Lion”). These are still the same Character for uniqueness.