The party's top leaders have approved the launch of a corruption investigation into the elder son of He Guoqiang, a former member of the supreme Politburo Standing Committee, four sources familiar with the matter told the South China Morning Post.
The son, He Jintao, is now under house arrest.
Wang Qishan, who is in charge of the Central Commission for Discipline Inspection, the Communist Party's anti-corruption investigation department, has briefed He Guoqiang on some of the initial findings, the sources said.
He Guoqiang was Wang's immediate predecessor as head of the anti-graft commission and was the eighth most senior official in the party before his retirement in 2012.
It is not clear if a younger son, He Jinlei, is also under investigation. The inquiry into He Jintao did not mean his father was implicated, the sources added.
The case contrasts with the corruption investigation into the former security tsar Zhou Yongkang , who was also a member of the Politburo Standing Committee. Zhou's elder son, Zhou Bin, was detained as investigators focused on Zhou Yongkang himself.
He Guoqiang, 70, once headed the powerful Central Organisation Department that controls more than 70 million Communist Party appointments and assignments across China. He also served as the party chief in Chongqing .
Sources said Wang had advised He to persuade his son to cooperate with the investigation. It remains unclear if the son will eventually face criminal charges - the sources said it would depend on the final findings of the investigation and his level of cooperation.
President Xi Jinping is believed to have made the final decision to launch the investigation, two sources said.
The president urged Wang to "get to the bottom of it" when he was briefed on the corruption investigation into Song Lin , former chairman of the state-run conglomerate China Resources. He Jintao is said to have played a part in the case.
The investigation into Song came after he was accused in June by two mainland reporters of misconduct and corruption over coal mine acquisition deals in Shanxi province, but it was only last month that Beijing announced a formal investigation into his affairs.
After Song's detention, the Guangming Daily, which is controlled by the party's central propaganda department, raised questions over the case and implied the former executive was protected by a senior leader.
"Who was responsible for withholding the top leadership's order to investigate Song for nearly a year? Who resisted against the probe?" the newspaper said in an editorial.
Xi's decision to push the investigation into He's son showed his determination to weed out corruption that is undermining the foundations of communist rule, the sources said.
The case would also send out a powerful message that family members or close associates of senior leaders would no longer be spared from investigation, even if the former top politicians themselves were not under scrutiny.
"Top leaders believe the runaway corruption among relatives or secretaries of senior leaders will sabotage the party's rule if things continue," said one of the sources. The leaders had reached a consensus in the He case in light of the investigations into Zhou and his family, the source said.
It has been revealed that many secretaries and relatives of Zhou were involved in allegedly illegal acts.
One of the sources said the president would face some "tough battles" ahead as he pressed his campaign against corruption, but Xi also understood he had to continue for the party to clean up its image and consolidate its rule.
The president has repeatedly stressed the importance of "zero tolerance to corruption" since taking office and he sees graft as the major threat to the party's legitimacy.
He Guoqiang's last public appearance was at an alumni event at the Beijing University of Chemical Technology in September. He also published a book in January, a compilation of his speeches and essays on building the party written during his tenure as head of the anti-corruption commission.
An article published by the Hong Kong-based magazine Phoenix Weekly the same month praised He as honest and upright, saying his sons' weddings took place at a simple guest house.
The article quoted his unnamed secretary as saying that He urged his family to "be honest" and behave themselves. It also said his secretary felt safe working with him because he was an uncorrupt official.
Zhou ranked beneath He in the party hierarchy before his retirement in 2012. The outcome of his case has yet to be made public and is awaiting a final decision from the top leadership.