See how often they participate in the script: HERE.
Character Story: Beth is the daughter of Sera and Hanch, the shop owners in Ordon Village. She has a slight crush on Link and is the reason he buys a slingshot. She grows throughout the story, helping both Renado and Link whenever they need it.
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.