Mary Yvonne "Sis” Sheehan, aged 93 passed away peacefully on September 8, 2021 at Marian Manor Nursing Home in South Boston. A resident of Dorchester, she was a bookkeeper for a variety of companies in Boston and a lifelong lover of ballet. Mary was predeceased by her brothers John J. Sheehan Jr. and H. Leo Zschau. She was the loving aunt of John J. Sheehan III and his wife, Lucy G Hutchinson of North Andover, David P. Sheehan, and his partner Keith Garton of South Egremont, Leo Zschau and his wife Elizabeth of Marlboro, Gerard Zschau and his wife Linda of Raynham, and Annette Atkinson and her late husband Dick of Hollis, NH. Her great nieces and nephews include Kathryn Sheehan, Elizabeth Sheehan, Stephen Zschau, David Zschau, Patricia Zschau Wild, Paul Atkinson (deceased), Nancy Atkinson, Michael Zschau and Robbin Zschau Hall. "Auntie Sis," as she was known, was a bright and independent soul who made every family gathering memorable. Mary will be interred at a Saint Joseph’s Cemetery in West Roxbury at a private family burial service.