Harry's Family History

It seems that this 7th and final Harry Potter book will finally reveal more about his family. On more than one occasion, Harry has worried that there are many similarities between himself and Voldemort. Harry Potter and the Half-Blood Prince describes Voldemort's parentage. As far as looks go, both Voldemort and Tom Riddle, Sr. are said to have features similar to Harry (dark hair, handsome). Could Tom Riddle Sr. have also been the father of James Potter or possibly one of Harry's grandparents? If so, that might explain the connection between Harry and Voldemort (speaking Parseltongue, how Harry managed to survive Voldemort's killing curse).