Former Russian paratroopers shove gay rights activist Kirill Kalugin aside to stop his one-man protest in St. Petersburg on Aug. 2. The former servicemen were gathered in central St. Petersburg to celebrate Russian Paratroopers Day. (ALEXANDER DEMIANCHUK/Reuters)

The leaders of the Group of 20 nations meet this week in a reconstituted 18th-
century palace just outside St. Petersburg. Almost entirely destroyed during World War II, it is more a replica than a reconstruction. But if there’s a ghost from the past walking its marbleized halls, it’s surely that of the palace’s most prominent former resident, Grand Duke Konstantin Konstantinovich Romanov.

Born there in 1858, Konstantin became a leading figure in Russian culture: a poet, a translator, a patron of the arts, an actor, the president of the Russian Academy of Sciences. A tall, slim, gentle man with a red beard, he was at home in the world, and a favorite of his younger cousin Czar Nicholas II, because he was so genuine and unpretentious — rare qualities among the Russian nobility.

But in today’s Russia, Konstantin is an inconvenient hero. Although he married young and had nine children, he was indisputably bisexual. He confided in his diary about his affairs with young men and his visits to a male brothel in St. Petersburg.

More than a century later, homosexuality is under siege in Russia. This year, President Vladimir Putin signed into law an act that bans the distribution of information about “non-traditional” sex to children. Critics, including Tanya Lokshina of Human Rights Watch, have called on President Obama and other leaders to speak out against the law while they are in Russia for the summit.

An American group called Human Rights First has urged Obama to meet with LGBT activists in St. Petersburg during his 30-hour visit, which begins Thursday. He has scheduled a meeting with representatives of various nonprofit groups for that afternoon.

Konstantin was not brazen about his bisexuality. In his diary, he anguished about having “sinned.” Yet he was a tolerant and gracious man. He carried on a warm correspondence over many years with the composer Peter Ilich Tchaikovsky, who set some of the grand duke’s poems to music in pieces he called “Romances.”

Tchaikovsky, who was gay, is another difficult hero. A movie about him due out next year, with Kremlin backing, will portray him as, at the very least, not gay, according to an interview with the director that appeared in the newspaper Izvestia. That news has caused a stir. It is not clear whether the director is crafting a piece of propaganda or is simply wary that an honest portrayal of the composer might leave him liable to prosecution for promoting a gay lifestyle.

Sexual proclivity aside, there’s another problem with the grand duke. Growing up in Strelna on the Gulf of Finland in what’s called the Konstantinovsky Palace, named for a forebear, and returning there for many summers, he developed an interest in natural history and literature. It was no small honor when he was named president of the Russian Academy of Sciences in 1889.

But the academy is under assault by Putin’s government. Still the primary engine for scientific work in Russia, it has become a hidebound, doddering institution that many scientists consider badly in need of reform. Yet the Kremlin’s reforms consist chiefly of trying to assert direct control over the academy and seizing its large property holdings. Even the academy’s strongest critics have spoken in its defense.

Konstantin would have been among them.

But he lived in a different era, when the nobility, at least, moved freely and comfortably among the nations of Europe. Konstantin reached the United States while serving as a young naval officer. He translated the classic German poets into Russian, as well as Byron and Shakespeare. Leaders were expected to have a cosmopolitan and cultured view of the world.

That has gone out of fashion in Russia, where Putin’s prosecutors have been harassing nonprofit groups in a search for “foreign agents” and where Western ideas of free speech, religious tolerance and, yes, rights for the LGBT community are often disdained.

Konstantin’s world exploded in 1914. He was in Germany that summer, taking a cure (with his German-born wife). After war broke out, they made their way, with some difficulty, back to Russia. But a son, Oleg, and a son-in-law were killed that year, and in 1915, the grand duke died in ill health.

Three other sons were killed by the Bolsheviks in 1918. The rest of his family scattered. His last surviving child, Vera, died in Nyack, N.Y., in 2001, at age 95.