Who is Frederick Hale from North and South and what is their importance?

Frederick is Margaret's brother. The British government want to hang Frederick for leading a mutiny on a British ship and he cannot come back to the country. Leonards almost catches him when Frederick risks his life to see his dying mother, but he manages to escape back to his wife, Delores, in Spain. Towards the end of the novel, Henry Lennox tells Margaret that Frederick visited him in London for a second time.