Cosco did not return calls seeking comment.

For Taihong, it was a blockbuster purchase. By 2007, when the price of Ping An’s stock peaked, the 159 million shares were valued at $3.7 billion — though by 2007 Taihong had already significantly reduced its stake, according to public filings.

While Taihong was the shareholder of record, the beneficiaries of the Ping An deal were cloaked behind more than a dozen investment vehicles controlled by the relatives of Mr. Wen, including two brothers-in-law, a sister-in-law, as well as several longtime colleagues and business partners of his wife, Zhang Beili, according to corporate and regulatory documents. All of them were listed, along with Ms. Duan, as the owners of Taihong.

And by 2007, the prime minister’s mother, who is now 91, was listed on public documents as holding $120 million worth of Ping An stock through a pair of investment companies linked to Taihong.

Ms. Duan, who says she got to know the prime minister’s family in 2000, said that she bought the Ping An shares for her own personal account. The Wen relatives only appear in the Taihong shareholding records, she said, because her company borrowed the government-issued identity cards of other people — mistakenly, she said, from relatives of the prime minister — to help mask her own Ping An stake from the public.

“In the end,” Ms. Duan said, “I received 100 percent of the returns.”

The Fallout

In 2001, China issued new regulations that put restrictions on trading in listed shares by Communist Party members and their families.

For instance, the rules barred party officials in charge of a state-owned company from using their parents, children — or even their children’s spouse’s relatives — to trade stocks of a listed state-owned company.

The Times found no indication that Mr. Wen shared inside information with family members.

But there are many unanswered questions about the relatives’ holdings, analysts consulted by The Times said, like who might have known about the relatives’ purchases and whether anyone had a legal obligation to disclose that information.