In March, Forbes magazine put Hans Rausing Sr. at No. 88 on a list of the world’s richest people, with a fortune of about $10 billion. The profile said that Mr. Rausing sold his share of the business to his brother, Gad, for an estimated $7 billion in 1995, and that to avoid punitive Swedish taxes had moved to a 900-acre estate in rural East Sussex in southern England.

Hans Kristian Rausing, or Hans K. as he is known in the family, is one of three children. He seems never to have had a serious job. As a young man, he went off on the so-called hippie trail to India and Katmandu while his sisters both pursued advanced academic degrees and devoted themselves to philanthropy. Lisbet, the oldest, runs a charitable trust called Arcadia with her husband; Sigrid, the middle child, distributes $30 million a year through her own trust and owns the literary magazine Granta and its publishing arm, Granta Books, as well as Portobello Books. Friends say that it is a given that her brother is very ill, and that she never refers to him except when she talks about raising his children.

“There’s absolutely nothing flashy or ostentatious about her at all,” said one publisher who knows her through the book world, speaking on the condition of anonymity. “She strikes you as someone who thinks very deeply about culture and is working hard not to be trivial.”

The Kemeny family said they were devastated by Mrs. Rausing’s death.

“In her short lifetime, she had a huge philanthropic impact, supporting a large number of charitable causes not only financially but using her own personal experiences,” her parents said in a statement. “She bravely fought her health issues for many years.”