Just came across your question about the Posthumus-families. You're right that finding remote relatives is something like finding a needle in a heystack.
I found several families Posthumus coming from Brielle and Harlingen (my line), again Harlingen, Lemmer (with possible connection to my line as the crests are the same!), Schiermonnikoog, Workum (Hans' line) Leeuwarden and Dokkum. In short all places in Friesland.
I just reived word from the community of Rotterdam that a Johan Willem Posthumus, born 20 october 1909, lived at the address Leopoldstraat 3B in Rotterdam moved to Barendrecht op June 28th 1961. This Johan Willem Posthumus wrote a letter in 1956 to the Dutch State Archive at Leeuwarden in the Dutch provincie of Friesland, the archive of which Hans Posthumus gave you the website. In this letter he describes the same ancestors as I am looking for. After the reply from the archive in the beginning of 1957 he fanishes into thin air again.
Do you have any genealogical websites in Canada where the name Posthumus is mentioned?
I would really appreciate your answer. Could you Geroge please get back to me at my private address firstname.lastname@example.org?