Who is Kit Sparrow from Ahab's Wife, or, the Star-gazer: A Novel and what is their importance?

Kit Sparrow is a sailor who was born on Nantucket. He first meets Una when she is sixteen and he and Giles arrive at the island. His mother, Hester, is a baker, who filled in for his father who went to visit his parents in England. When his father returns, his mother develops an affliction of the mind and is sent to live on a sheep farm, where she dies. Kit, along with Giles, works on the whaling boat Sussex. Una follows them to the boat and secures a position as a cabin boy. Kit and Giles recognize her on the boat. When the Sussex is abandoned after a whale attack, Kit is in the smaller boat along with Una, Giles and ten others. When they run out of food and water, they resort to cannibalism to survive. Kit, along with Giles and Una, are the only survivors rescued by the Alba Albatross.