Steve and Mike, I believe yas are right to an extent, but can you imagine a mother saying 'Now listen Janos my son, if the kids start hassling you in school, don't take it personally. It's just that your father was Vlad the Impaler and they're all orphans because of him...' ?
I'm no DNA expert, but isn't their a chance that a son of Hitlers would share DNA markers that are familiar to other close relatives of Adolph? In other words...all Hitler males might share some DNA?
Maybe not a 100% match, but it could narrow the odds on weather he is correct in his assumption...