Asked about his business deals and the wedding, Kirill Shamalov and Sibur declined to comment.

The trajectory of Kirill's fortunes sheds new light on how people close to Putin have taken commanding positions in key companies - and how such opportunities are now being extended to a new generation. Like the wedding, much of this transfer of riches has occurred away from public scrutiny.

Vladimir Milov, a former Russian deputy energy minister and now an opposition campaigner, said Putin's friends had acquired major assets with the help of lenders with links to the state, such as Gazprombank.

"It's extremely non-transparent, so it is hard to get to and judge the specifics of the loan agreements," Milov said. "They consider Gazprombank their pocket bank."

He added: "They are looking to pass on their power and privileges to a new generation."

Asked about the wedding celebrations and business deals, Dmitry Peskov, spokesman for the Russian president, said: "Putin's daughters are not involved in politics or business. The businessman, Shamalov, is well known. As far as we are aware, all his activities are in line with the laws of the Russian Federation. For many years he has been in the management of the company Sibur, and along with other senior managers is a shareholder. His career and business are not within the sphere of interest of the Kremlin. We do not give comments on the private lives of Putin's close relatives."

The Brothers Shamalov

When Kirill Shamalov was growing up in the 1990s, his father, Nikolai, was a co-founder with Putin and others of a development of dachas known as The Ozero (Lake) Cooperative, about 100 km (60 miles) north of St. Petersburg. Various members of the Ozero development went on to prominence in Putin's Russia.

Nikolai Shamalov became a shareholder in a small lender called Bank Rossiya, which over the past 15 years has grown to be one of Russia's most influential banks. Kovalchuk, the co-owner of the Igora ski resort, is the largest Bank Rossiya shareholder.

After Russia seized control of Crimea in 2014, the United States sanctioned Bank Rossiya, describing it as the personal bank of the Russian elite. The European Union sanctioned Kovalchuk and Nikolai Shamalov for their close links to Putin. The U.S. Treasury also sanctioned Kovalchuk as a member of Putin's inner circle.