Lina was Anna and Elsa's youngest sister. She was kidnapped from the castle at just four months old, right after their parents died. It's been 2 years. The sisters never stopped hoping she would return but one day a 2 year old girl, exhausted, dirty, starved, beaten, and sick with pneumonia appears back in Arendale. Nobody knows who she is at first because the filth. Lina had been beaten and starved by the clan that tried to attack Elsa when she had started showing her powers. Nobody knew that yet. Lina has a photographic memory that she was born with. Elsa and Anna had taken turns caring for her until she had been kidnapped.