They didn't create a family-run banking dynasty like the Rothschilds or the Warburgs. They don't even work at the same bank, and both are quick to point out that they serve their shareholders. But the Grundhofer brothers' rise to become chief executives of two of the largest banks in the country is a remarkable story.

What did mom put in their oatmeal?

Born to working-class parents in Southern California on opposite ends of World War II, John F. Grundhofer and his younger brother, Jerry, each worked his way up in the banking industry. Jack, 61, runs $77 billion-asset U.S. Bancorp in Minneapolis. Jerry, 55, runs $74 billion-asset Firstar Corp. in Milwaukee.

The rivalry is fierce but friendly, though the brothers themselves refuse to draw comparisons. "They are intensely ambitious," said Carl E. Reichardt, former chief executive officer of Wells Fargo & Co. in San Francisco, where both brothers were groomed in leadership. "They are also as close as brothers can be."

Jack chalks it all up to fate. "We stumbled into banking," he said in a recent interview. "The opportunities presented themselves."

Examining the pattern, it would be easy to conclude that younger brother Jerry was eager to match the accomplishments of Jack. Both graduated from Loyola Marymount University in Los Angeles. Jerry started his career in the mailroom at Union Bank, where his brother was already a management trainee. Both eventually jumped over to Wells Fargo. Both have built their companies through mergers.

"I've always been very proud of Jack," Jerry said. "And I've always wanted to be all I could be."

Observers have enjoyed speculating about what would happen if one brother bought the other one's bank. Until recently, the game more frequently put Jack at the controls. But in December, U.S. Bancorp warned of lower fourth-quarter profits because of sluggishness in consumer lending operations. Suddenly, Firstar, with a market capitalization of $18.9 billion, became the favorite to buy U.S. Bancorp, which has a market cap of $15.5 billion.

Would they ever work together again? Avoiding a direct answer, Jack laughed and said, "We have worked together on an off, and we enjoy each other personally."

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