Among the most compelling of Nicholas Nixon’s series of photographs are the portraits that he has made of his close-knit family. These photographs, taken over time, explore the nature of long-committed relationships. The exhibition features the entire sequence of the celebrated portraits of the artist’s wife, Bebe, and her three sisters. Taken annually, the Brown Sisters pictures reveal gradual changes in their physiques and shifts in their relationships. The exhibition also includes photographs of the artist’s daily life with Bebe and their children Samuel and Clementine (born in the early 1980s), which enable viewers to share in the daily interactions and joys of parenthood. Also included in the show are recent portraits of Bebe and self-portraits that stand for the steadiness of long marriage. Nicholas Nixon, who teaches at Massachusetts College of Art, is one of the most celebrated American photographers of our generation. The Brown Sisters photographs are a promised gift of James and Margie Krebs. Many of the other works in the exhibition are loans from the photographer.