BEIJING — When Maoists were trying to keep control of China in the 1970s, a powerful general from the south came to the aid of moderates, helping to arrest the radicals and throw them in jail. The bold actions of the general, Ye Jianying, paved the way for the country’s move to a more market-oriented economy, and created a political dynasty that still plays kingmaker, able to influence national policy and protect its sprawling business empire in southern China long after his death.

Over the past year, according to party insiders familiar with the situation, members of Mr. Ye’s family have helped organize meetings to criticize the country’s current course and have influenced top military appointments while helping block a vocal economic reformer from joining the Politburo Standing Committee, the small, powerful group at the top of the party hierarchy, because they felt that he was not attentive to their interests.

The rise of so-called princelings like the Ye family will reach a capstone this week, when Xi Jinping, himself the son of a Communist Party pioneer, is to be unveiled as China’s top leader at the conclusion of the 18th Party Congress. Mr. Xi is likely to be joined by at least two other relatives of senior leaders on the seven-member Standing Committee.

Despite rising controversy over their prominent role in government and business — highlighted by recent corruption cases, as well as the fall of Bo Xilai, whose wife was found guilty of murder — China’s princelings, who number in the hundreds, are emerging as an aristocratic class with an increasingly important say in ruling the country.