WASHINGTON The big sister is the first deputy assistant secretary of state ever to have her own Secret Service detail, after having passed up lucrative offers to become a television commentator for the privilege of promoting democracy in the Middle East. The little sister may well be the first previously unknown presidential campaign aide to earn a million-dollar advance for her memoirs.

But Elizabeth and Mary Cheney are no ordinary siblings - and their parents, Dick and Lynne, are no ordinary mom and dad. Like the Adamses, Roosevelts, Tafts, Kennedys, Gores and Bushes before them, they are a family act. They are a foursome fully immersed in conservative politics and public policy.

In February, Liz, 38, was hired as the No. 2 official in the Bureau of Near Eastern affairs at the State Department, her second tour in the region. In March, her husband, Philip Perry, was nominated to be general counsel for the Department of Homeland Security.

That same month, Mary, 35, agreed to write about her role in running her father's re-election campaign last year and her life as the first openly gay member of a Second Family.

Dick Cheney may be most influential behind the scenes, but his daughters are increasingly out front. It is a role that Lynne Cheney, whose most recent children's book came out last autumn, describes as a natural evolution.

"I just think they were always part of campaigns," Lynne Cheney said in a rare telephone interview the other day. "It seemed like kind of the healthy way to do it, to not leave them home with a baby sitter but to take them along."

Over the past 25 years, the scope of the family's influence has grown from a congressional seat from Wyoming to the inner circle of perhaps the most influential vice presidency in U.S. history.

Such extraordinary blending of family careers and the nation's business has generated controversy. A Pittsburgh Post-Gazette editorial, for example, condemned Perry's nomination to the Homeland Security post, which pays about $140,000, as "a pure form of nepotism not usually seen in American government" and complained that Liz, who earns $149,2000, "also feeds at the government trough."

Edward Walker Jr., who headed the State Department's Near Eastern bureau at the end of the Clinton administration, noted a long tradition of bringing political appointees into the bureaucracy.

"Sometimes they are good and sometimes they are bad," Walker said, adding: "Liz is a little different, obviously, because of the name. But the name doesn't bother anybody I know, simply because she did her job."

Adam Bellow, a son of the novelist Saul Bellow and author of a 2003 book, "In Praise of Nepotism: A Natural History," explored society's long-standing ambivalence about the issue. He noted that the Founding Fathers had been skeptical of British notions of entitlement, but "they all bent over backwards to help their family members."

Bellow said that families like the Cheneys "had better be prepared for all kinds of scrutiny."

Supporters of the Cheneys, including some prominent Democrats, note that both daughters have built their own reputations, while Perry did the same as general counsel to the White House Office of Management and Budget in Bush's first term.

He was moved to Homeland Security by its new secretary, Michael Chertoff, his former law partner at Latham & Watkins, where he represented Lockheed Martin in dealings with the department.

Mary Matalin, a longtime political adviser to Cheney whose new publishing imprint at Simon & Schuster acquired Mary Cheney's memoir, allowed that "nobody ever really understands any of them, because they're not about trying to be understood because they're too busy trying to do what they do."

The Adamses and Bushes produced father-son presidents, the Tafts a father-son president and senator combination, and the Kennedys a trio of brothers followed by cousins in the family trade.

In World War II, all five of Franklin D. Roosevelt's children were either in uniform or held unofficial jobs helping their father, while Al Gore's eldest daughter, Karenna, played a central role in his presidential campaign in 2000.

Carl Anthony, who has written extensively about presidential families, said the Cheneys were products of the women's movement.

"Even if you're a traditionalist, conservative Republican, women have benefited," he said, "with not only the wife but the daughters pursuing such an active role in the intellectual and political life of their father, and not just in a private way."