Texas and Saudi Arabia have much in common. Oil. Vast tracts of scrubland. And political dynasties. No wonder King Abdullah is the only foreign leader to have two bilateral meetings with George Bush at the president's sun-baked Crawford ranch.

If conversation about OPEC or Middle East peace lags, they can always turn to what it is like to follow Dad's footsteps to the top. They belong to what historian Wolfgang Schivelbusch labels the "postheroic generation" of victors' sons -- leaders who are called on to "preserve their fathers' achievements" and to "produce great deeds of their own."

Actually, I would be amazed if they did talk about that; sons of famous fathers usually hate the subject. But they should talk about it. More to the point, their citizens need to talk about and weigh the pluses and minuses that political nepotism creates.

Americans turned to a father-son combination for two of their past three presidents, and now flirt with moving the Clinton family back into the White House. Somehow, American presidential politics is all in the family at the moment. That has happened before, with the Adamses, the Kennedys and others. But the willingness to go with brand names is more pronounced today, and it occurs in more challenging times.

Abdullah's ascension to the throne two weeks ago also raises fresh questions about the durability of Saudi Arabia's unusual succession system, which keeps power in the family but away from the next generation.

The Saudi and American experiences are vastly different, of course. Bush inherited name recognition and an insider position in the Republican Party from his president-father, not a throne. He twice had to make his own way to the White House. And Bush at 59 is two decades younger than Abdullah, whose father, Abdul Aziz ibn Saud, founded the kingdom in 1932.

But they have each come to power in the shadow of a father's large accomplishments. While Americans were not impressed enough to reelect him in 1992, George H.W. Bush will reside in history as the president who ended the Cold War and guided an effective Western reaction to German reunification and Soviet disintegration. That is not nothing, as his son recognizes.

I have always been struck by the emphasis that George W. Bush immediately placed at the outset of his first term on his duty to remove the final traces of the Cold War. He termed the arms control treaties and nuclear arsenal he inherited obsolete artifacts of an era he would demonstrate had ended. He would move America beyond not just Bill Clinton but also that president before Clinton.

Then came Sept. 11, 2001, and the creation of a mission that President Bush could claim as uniquely his own. The war on terrorism is a "generational" task for heroes, the president has repeatedly said in rhetoric suggesting that it has fallen to the son to save the nation.

Abdullah is the fifth son of the Saudi founder to become monarch over the past half-century. He is due to be followed not by one of his sons but by a brother, who will be only a few years younger than Abdullah is, and so on until in theory at least all 24 of Abdul Aziz's surviving sons have had a shot at being king. (Seeing marriage as being as important as the sword in bringing the territory's tribes together, Abdul Aziz took as many as several dozen wives and sired several score sons.)

The Saudis want to defy the predictions of Ibn Khaldun, the Islamic historian who wrote in the 14th century that Arab dynasties rise and fall like family fortunes: The first generation takes power, the second consolidates it, the third uses it to live in luxury and licentiousness, and the fourth generation squanders it all as new and hungry forces sweep in from the desert.

The Saudis love their children so much they want to spare them, for as long as they can, the burdens of ruling. But it becomes increasingly difficult to square that instinct with the 21st century's love of instantaneity.

Another downside of dynasty is pointed out by Schivelbusch: Outsized pressures on political heirs to perform greater feats can lead to dangerous overreaching. "Where there is no space left to build, the only option is to tear down." Imperial Germany at the turn of the 20th century is his example of "destructive heroism."

The Bushes, father and son, are not given to such high-flown theorizing. But if Americans insist on perpetuating family rule, we need to think and talk about all its aspects. Even if the son-king and the son-president do not.