As the website says, there is nothing certain known about John Alden's parentage. Priscilla Mullins' father William, mother Alice, and brother Joseph all came to Plymouth and died the first winter. According to the silver book, William Mullins' parents were John Mullins and Joan Bridger. According to The Great Migration Begins, his probable origin was Stoke, Surrey, near Dorking. There are several articles in The Mayflower Descendant that address these questions.
Karen