Who is Kaarlo from Our Only May Amelia and what is their importance?

Kaarlo is May Amelia's seventeen-year-old cousin, who has been raised as her brother since he was ten years old. Kaarlo's mother is Pappa Jackson's sister. When Kaarlo's family decided to move to Canada, they could not afford train tickets for all their children. The family decided to leave Kaarlo with Pappa Jackson until they could afford to send for him. Seven years pass and the family does not send for him. When Kaarlo argues with Pappa Jackson about his desire to move to Astoria, Pappa Jackson tells him that his entire family died six months before in a fever epidemic. Kaarlo is heartbroken by this news, but eventually resolves to respect and remain a part of the Jackson family.