Since posting that message I've bought Song of Courage, Song of Freedom by Marilyn Sequin, and The Beaded Moccasins by Lynda Durrant. Both have lots of detail about Mary Campbell's kidnapping, but are pretty skimpy on family details. Can you recommend any other books?
As for Joseph Willford, I know about his conviction for horse theft in England and subsequent exile to the colonies. Do you have more on his background?