It is my understanding that much time and money has been spent trying to explicitly answer your question but without total success. There is a book named "The Frothingham Genealogy" available from Higginson Books, authored by Thomas Bellows Wyman & Richard Frothingham which attempts to answer the question. The availability of additional information since the book was written causes one to question some of his data. I have some additional printed matter that I will share if you are interested. From what line do you descend?