In a preview of Oliver Stone’s documentary “The Putin Interviews,” Russian President Vladimir Putin drops a bombshell. Asked by Stone if he has grandchildren, Putin smiles and answers “yes.”

Questions about Putin’s personal affairs are Russian media’s most explicit no-go area. The makeup of the country’s first family remains a mystery. State media are under strict instructions to never mention Putin’s daughters or ex-wife, unless commanded to do so. News outlets that find the courage to investigate, for example, Putin’s daughter or her miraculously wealthy husband, paint a target on their own backs.

Barred from asking the question themselves, Russian journalists were obliged to wait until Putin opened up to a complete stranger — a foreigner — to report that he was a happy and loving grandfather.

In the same interview, Putin tells Stone that the Kremlin does not control Russia’s media.

The irony will be lost on few Russians. After all, it is the same Vladimir Putin who, in late 2013, signed an executive order to gut the country’s leading news agency and appoint a hyper-loyalist TV host as its director. It is the same Vladimir Putin whose aides publicly say journalists working for state-owned outlets are expected to toe the government line.

Stone never challenges Putin on the obvious implausibility of his claim.