The information concerning Jon de Purvaince came from Daryl Johnson, who is listed under www.rootsweb.com as "Daryl Johnsons Tree". His email is..... firstname.lastname@example.org. He has quite alot of information listed about that family, and I am sure you would enjoy it. I also found the dates from Genealogy.com.
I am tracing that line because Jon and the others on that list are my uncles. I can tell by your last name of course that you are in that direct line. My family was originally Gonce's out of France and some parts of Germany.