He last remaining living member of Trollbane bloodline. Its automatically makes him Stromgarde's future king.
Quote from wowpedia:
Fist and bird both are symbols of Stromgarde. I personally would choose fist but Blizzard choose bird probably because fist already used by Silver Hand.
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Trollbane are not from Thoradin's bloodline. The only one who can ask for Strom'kar is Anduin Lothar.
Trollbane have their own family weapons - Trollbane Axe and Trol'kalar Sword.
Trollbane family descend from Ignaeus Trollbane - one of Thoradin's friends and generals:
Sorry for big picture - i'm just hyped for Stromgarde.