Bernard Berenson, art historian and critic, was born in Lithuania in 1865. His family moved to Boston, Mass. in 1875 where he was enrolled in the Boston Latin School. He then attended Boston University for one year, and graduated from Harvard College in 1887. Encouraged by Isabella Stewart Gardner and others, Berenson travelled to Europe to study art, although with the original intention of becoming a writer. Mary Berenson was born a Quaker in Germantown, Pennsylvania in 1864, the daughter of well-known preachers Hannah Whitall and Robert Pearsall Smith. She attended Smith College from 1882-1884 and the Harvard Annex for one year, 1884-5. She left the US to marry Irish barrister and political hopeful B.F.C. "Frank" Costelloe in 1885, which also necessitated her conversion to Catholicism, against the advice of her family. Mary and Frank had two daughters, Rachel (Ray), born in 1887 and Karin, born in 1889. Both were diffìcult pregnancies. Mary's family followed her to England shortly afterwards and became deeply involved in social, literary and cultural circles. In 1890 Berenson was introduced to Mary through a mutual friend, Gertrude Hitz-Burton. Having already become unhappy in her marriage, Mary followed Berenson back to the continent to study art under his tutelage. She eventually left her husband and lived in Italy and travelled with Berenson. A year after Frank Costelloe's death in 1899 Mary and Berenson were married in Italy (Dec. 1900). In spite of numerous affairs and liaisons on both sides they remained married their entire lives. Having maintained separate residences until their marriage, in 1901 they moved into "I Tatti," a villa owned by John Temple-Leader. They purchased the property in 1908 from Temple-Leader's son, who had inherited it upon his father's death. They spent several years updating, renovating and adding to the villa, especially the library and gardens, work supervised by Cecil Pinsent and Geoffrey Scott. They continued to acquire adjacent properties. Berenson had gone to Europe after college with the intention of becoming a writer. There, he was drawn in by the aesthetic experience, and became more focused on looking at and writing about art. As his reputation as an "expert" was established from his scholarly publications, Berenson was often requested to provide his attributions on works of art for various art dealers, private collectors and museums. One of the most notable of these relationships was with Duveen Bros. Mary initially became involved in the women's movement in England and America, and continued in her political activities, making speeches and helping her first husband with his campaigns for office. After meeting Berenson, however, and based on her studies with him, the focus of her energies shifted, and she also became an art critic. She worked very closely with Berenson on his projects, as well as publishing substantially on her own.
Elisabetta "Nicky" Mariano was hired in 1919 as librarian/secretary. She was a close friend of both Mary and Bernard. Althought they did not marry after Mary's death in 1945, Nicky remained a close companion to Berenson until his death in 1959. She continued to live in a house on the property and served as an informal advisor to the early directors of the Harvard University Center until her death in 1968.
For more extensive biography, see Ernest Samuels's two volumes, Bernard Berenson: The Making of a Connoisseur (Cambridge, Mass.: Harvard Univ. Press, 1979) and Bernard Berenson: The Making of a Legend (Cambridge, Mass.: Harvard Univ. Press, 1987). Other biographies include Nicky Mariano, Forty Years with Berenson (New York: Knopf, 1966), Sylvia Sprigge, Berenson: a Biography (London: G, Allen & Unwin, 1960), as well as numerous published diaries and letters. For more information on Mary Berenson see Barbara Strachey and Jayne Samuels, eds., Mary Berenson: A Self-Portrait from her Letters & Diaries (London: V. Gollancz, 1983) and Robert A. Parker, The Transatlantic Smiths (New York: Random House, 1959).
From the guide to the Berenson, Bernard and Mary. Papers, 1880-2002, 1880-2002, (Biblioteca Berenson, Villa I Tatti - The Harvard University Center for Italian Renaissance Studies)