I found a site in German. The author claims that a Nazi scientist, named Karl Klauberg, who developed a technique for artificial insemination, saved Hitler's sperm.
He escaped prison after WW2 and found refuge in East Germany. He was allowed to stay since he shared his scientific work with the authorities and he also handed over the frozen sperm of Hitler.
He than allegedly transferred Eva Braun's sister from West Germany to East Germany for insemination with Hitler's sperm. Allegedly this was part of a secret pact, between Russia, US, and the Vatican, to gain world domination. The three parties agreed that Angela Hitler should lead a supranational conglomerate of nations and that the succeeding Vatican must also be of German origin. Which happened to be Ratzinger.
She was raised by a Lutheran pastor.
Source: http:// noch.info/2015/09/stasi-und-kgb-angela-merkel-ist-tochter-von-adolf-hitler/