See how often they participate in the script: HERE.
Character Story: The first child of Uli and Rusl, Colin is quite shy and manages to be picked on by the other kids in town. He idolizes Link because he is tough and can use a sword. Throughout the plot, Colin grows to understand understand that being brave and strong comes in many different forms.
Race Story: Humans typically live peacefully with other races throughout all of Hyrule. The more specific Hylian race is a subcategory of humans. They can be differentiated by their ears -- Humans have rounded ears and Hylians have pointed ears.