Mr. Pritzker spent most of his life building with his two brothers. The Pritzkers founded the Marmon Group in the early 1950s, after taking out a loan to buy an unprofitable manufacturer of bicycles and hospital equipment. Mr. Pritzker’s older brother Jay became the Marmon Group’s deal maker, spotting undervalued companies to acquire, which Robert, the middle brother, then ran. A third brother, Donald, ran one of the few household-name companies in the increasingly far-flung empire, the Hyatt hotel chain. Donald Pritzker died in 1972, Jay Pritzker in 1999. The Pritzkers ventured into the hotel business in 1957 with the purchase of a property near the Los Angeles airport. Hyatt, which went public in 1962, grew slowly and quietly until 1967 and the completion of the Regency Hyatt House in Atlanta, which caused a sensation with its cascading fountains and glass elevators. Now considered the first of America’s modern atrium-style hotels, the hotel, later renamed the Hyatt Regency Atlanta, inspired many imitators and accelerated Hyatt’s growth. (The Pritzkers took the hotel business private in 1979 and 1982.) Mr. Pritzker was the grandson of Nicholas J. Pritzker, who arrived in Chicago from Ukraine in 1881 at the age of 10. Nicholas Pritzker worked at menial jobs, taught himself English, married and had three sons, and eventually earned a law degree. His three sons joined him at the firm Pritzker & Pritzker. It was Robert Pritzker’s father, Abram, known as A. N., who in 1935 began the family’s practice of placing business assets in trust, for the benefit of Nicholas J. Pritzker’s descendants. The family is in fact considered the wealthiest in Chicago, and Robert Pritzker is known for his large donations to local institutions, including the University of Chicago medical school, and his alma mater, the Illinois Institute of Technology. He served on the institute’s board and taught classes there, and at the University of Chicago and Oxford. In recent years the family drew attention when Mr. Pritzker’s two youngest children, Liesel and Matthew, filed a lawsuit claiming that he had removed assets from trust funds and directed them to other parts of the business. A settlement led to sales of some valuable Marmon units, including a public offering of Hyatt shares and, in 2008, the acquisition of 60 percent of Marmon by Berkshire Hathaway, Warren E. Buffett’s company. Terms called for Berkshire Hathaway to pay $4.5 billion for the first 60 percent, then buy the rest in stages. Robert Alan Pritzker was born in Chicago on June 30, 1926. He is survived by his wife, Mayari; five children, James, Linda, Karen, Matthew and Liesel; 10 grandchildren; and two great-grandchildren.