I’ve not seen an English-language equivalent or derivative of thomasmann.de. Unfortunately, the domain ThomasMann.com is taken, but you may want to start your own TM website; die domain ThomasPMann.eu is not taken, ThomasPaulMann.net is also available.
It appears that there is an English version of “Die Manns – Ein Jahrhundertroman”; siehe “The Manns - Novel of a Century” bei yhttp://www.imdb.com/title/tt0250573/.
Wikipedia also claims that this is an English version, see under Weblinks of the site http://de.wikipedia.org/wiki/Die_Manns_%E2%80%93_Ein_Jahrhundertroman
; but I haven't watched it myself and can’t verify it. Amazon.com doesn’t seem to have this title.