I read about him in John Toland's biography of Hitler.He was,I believe,the son of one of Hitler's half brothers and an Irish girl he was married to while working in England just before World War 1.
They went to Munich in the 20's and hit the Fuehrer up for money then went to New Jersey.He served in the U.S. Navy(not under the name Hitler),and his identity,which was known to the U.S. government,was protected.His first name,Ithink,was Patrick and I'm fairly certain he had children,which is why his assumed name has never been disclosed.
At any rate,Hitler had other nephews,indeed he still has some relatives in Lower Austria,at least the ones that didn't die in the gulag,as Stalin had a number of them rounded up after the war.A couple of his nephews were captured at Stalingrad,which they tried to exchange for Stalin's oldest son,who had been captured by the Germans.Stalin refused(he hated this oldest son by his first marriage,he was too Georgian)and his son ended up killing himself by running at the wire in the POW camp and getting himself shot.