SERIAL groper Thomas Kramer, the Miami developer recently arrested for fondling a 13-year-old boy in the Rainbow Room’s bathroom, has a familiar friend. The Post’s Braden Keil reports the German playboy is a pal of Matthias Von Wrede, the Hamptons real estate broker (also from Germany) busted last month for distributing child porn. The two had often e-mailed each other on their self-indulgent MySpace sites. Kramer, who has avoided prosecution for rape and other sex charges in the past, appears to be an equal opportunity lech now that a Florida woman has sued him for grabbing her breast at another party.