why doesn't james locate ruth's sister, dee-dee ?

When Ruth left Suffolk, she promised her youngest sister Dee Dee that she'd return there. She didn't, and Dee Dee never forgave her. Years later, Ruth tried to contact her sister and was reminded of that broken promise; she cut Ruth out of her life because of it. James probably could have found Dee Dee when he visited there, but he decided against it. He thought his visiting would only give her more pain, and so he stayed away.