Thanks. :) Ancestry.com has this book as "Genealogical Dictionary of New England Settlers." I've let my account lapse for now so I don't recall - does the book offer a hard source for a connection between John and William? Or is it conjecture?
Christine Van Kleeck's GEDCOM at Ancestry.comquotes the History of Salem, saying, "John Alderman dies 1657, apparently alone in the world, and having acquired a considerable estate, especially in live stock, he displayed in his will a real philanthropy for that time in giving his best cow to Rev. Mr. Norris of Salem, and a cow each to Rev. John Eliot, the Apostle to the Indians, at Natick, the Indians he preached to, Mr. Thacher of Marblehead, Rev. Mr. Whiting of Lynn, Rev. Mr. Walton of Marblehead, and Rev. Mr. Cobbet of Ipswich. One of his heifers he gave to Deacon John Horne of the Salem Church." (Note: I have not seen this History for myself.)
That whole 'alone in the world' thing at John's death in 1657 is the stickler - perhaps I'm misinterpreting it, though. I wonder if William might be a (possibly estranged) brother of John, making the ages more likely?
(Apologies if any of the above is unclear - I really shouldn't reply to messages when I've been awake for only 5 minutes, fueled exclusively by rather stale raisin scones.)