Nancy Bush Ellis, the sister of one president and aunt of another, who for a time devoted herself to Democratic causes despite her family dynasty’s Republican lineage, died on Sunday January 10 2021 at an assisted living facility in Concord, Mass. She was 94. Her son Alexander Ellis 3d said the cause was complications related to Covid-19. Unlike most of her family, Ms. Ellis was a liberal Democrat for decades, promoting environmental and antipoverty causes, raising money for the N.A.A.C.P. and serving as head of the New England section of the NAACP Legal Defense and Educational Fund.Ms. Ellis was a board member and honorary director of the Massachusetts Audubon Society. She raised money to establish the Rio Bravo Conservation and Management Area in Belize. She also served on the board of Pact, which fights poverty worldwide. Nancy Walker Bush was born on Feb. 4, 1926, in Milton, Mass., a Boston suburb. Her father, Prescott Sheldon Bush, worked on Wall Street before he was elected to the United States Senate from Connecticut in 1952. Her mother, Dorothy Walker Bush, energetic and forceful, raised Nancy and her four brothers to be modest and socially responsible but also highly competitive. She attended the private school Rosemary Hall in Greenwich (now Choate Rosemary Hall in Wallingford, Conn.) and Miss Porter’s School in Farmington. Conn., and majored in English at Vassar, from which she graduated in 1946. That was the year she married Alexander Ellis Jr., who would run the Boston insurance brokerage firm of Fairfield and Ellis. Ms. Ellis lived with her husband and four children in Concord. After her husband died in 1989, Ms. Ellis moved to Beacon Hill in Boston and led an active social and cultural life. In addition to her son Alexander, she is survived by two other sons, John Prescott Ellis and Josiah Wear Ellis, who is president and chief executive of the Denver Broncos; a daughter, Nancy Walker Ellis Black; nine grandchildren; 11 great-grandchildren; and a brother, Jonathan James Bush. President George Bush died in 2018. Another older brother, Prescott S. Bush Jr., died in 2010, and her younger brother, William H.T. Bush, died in 2018.