Kristoff

Kristoff was an ice harvester who, alongside his reindeer friend, Sven, was raised by the trolls. He generally kept to himself and only interacted with other humans when necessary, preferring the company of Sven.

As such, Kristoff only accompanied Anna on her quest to retrieve Elsa strictly as a business arrangement but would eventually develop feelings for the princess; to this end, he strove to ensure her safety as she worked to restore both summer and her bond with her estranged sister. After summer's return, Kristoff and Anna began a romantic relationship.

In Shadow and the Snow Queen
Kristoff isn't very welcoming of the other characters, usually only to Princess Anna. His personality is quite similar to Knuckles's, however...