Who is Danny Robinson from A Dangerous Fortune and what is their importance?

Danny is the brother of Maisie, whose family immigrated from Russia. Danny is thirteen years of age at the opening of the Prologue. He leaves for America by stowing away on a ship in the harbor when his father loses his job. He appears after seven years and locates Maisie through an ad in the paper, and then their parents. He has a plan for opening a business in London. His business goes bankrupt and Dan becomes a Member of Parliament. He lives with Maisie and Rachel at Maisie's house until Micky's death, when he marries Rachel.