"слушок, что не кто йной, как племянник..."
Правильно: "никто иной, как племянник". I'd say, phrase made this way indicates more certainty that "he" is, in fact, Zhukov's nephew.

... "it was none other than" both sound totally okay to me.
The construction "Rumor had it that..." is unfamiliar to me. Is it really correct?