Born Nedenia Hutton, December 29, 1925, in New York, NY; daughter of Edward F. Hutton (a stockbroker) and Marjorie Merriweather Post; married Stanley M. Rumbough, Jr., March 23, 1946 (divorced, December, 1966); married Cliff Robertson (an actor), December 21, 1966 (divorced, 1989); married Ted Hartley (a business executive), November 18, 1989; children: (first marriage) Stanley M. III, Nina, David; (second marriage) Heather. She was born Nedenia Marjorie Hutton on Dec. 9, 1923, in New York City and nicknamed Deenie. Her parents divorced when she was 10. She attended George Washington University, but dropped out after a year to study at the American Academy of Dramatic Arts in New York. In 1946 she married Stanley M. Rumbough Jr., heir to the Colgate-Palmolive consumer products fortune, and spent much of the next decade raising their three children. By the time she got her first movie role — as a young research assistant to Katharine Hepburn in “Desk Set” (1957), with Spencer Tracy — she was over 30. Divorced from Mr. Rumbough and married to the actor Cliff Robertson in 1966, she was partly responsible for bringing down the head of a Hollywood studio. When David Begelman, the president of Columbia Pictures, embezzled $10,000 by forging Mr. Robertson’s name to a check, no one paid much attention, Ms. Merrill said, until she called her friend Katharine Graham, the publisher of The Washington Post. With an inheritance from her parents estimated at more than $50 million, Ms. Merrill became a philanthropist. A liberal Republican, she was vice chairwoman of the Republican Pro-Choice Coalition, an advocate on women’s health issues and vice president of the New York Mission Society. After her son David, who had diabetes, died in a boating accident at age 23 in 1973, Ms. Merrill created a yearly award for scientific excellence in his name for the Juvenile Diabetes Research Foundation. After divorcing Mr. Robertson in 1986, Ms. Merrill married Ted Hartley, a former Navy fighter pilot, actor and investment banker, who survives her. Shortly after their marriage in 1989, their company, Pavilion Communications, bought a controlling interest in RKO Pictures, but they had little success in returning that studio to its former glory. In addition to her son and her husband, Ms. Merrill is survived by a daughter from her first marriage, Nina Rumbough Roosenburg; a stepson, Philippe Hartley; six grandchildren; four stepgrandchildren; and two stepgreat-grandchildren. Heather Robertson, her daughter with Mr. Robertson, died of cancer in 2007. Mr. Robertson died in 2011.