Lydia Lee is the Lee family's middle child and the "knot" that ties the family together. After Marilyn abandons her dream of becoming a doctor, she puts all her energy and effort into raising Lydia to be one. Similarly, after an isolated youth feeling like an outsider, James raises Lydia to be like everyone else—to blend in and be popular. Under the weight of such pressure, Lydia struggles to find her own identity, particularly when pressure mounts and she feels herself failing to meet her parents' expectations. After a series of "failures," Lydia decides to baptize herself in the lake, a symbolic gesture meant to signify her rebirth. However, Lydia drowns, and her death threatens to unravel the family ties completely.
Nath Lee feels like an outsider for many reasons. As one of the only Asian students at school (the other being his sister Lydia), Nath is regularly singled out and ostracized. He is smart, but his parents pay him little attention until he's accepted at Harvard University. In the final pages of the novel, the narrator also suggests that Nath is gay, which would further compound his feelings of isolation in 1970s middle America. Living in the shadow of Lydia's potential, Nath looks forward to exploring his independence and thriving at college. When Lydia dies, however, he realizes how much he valued their relationship and struggles to come to terms with his perceived role in her death.
James Lee's childhood, filled with isolation and ostracism, informs his character by explaining his obsession with "fitting in." He teaches American history, marries an average white woman, and raises his children not to ruffle any feathers, to care what other people think about them, and to challenge stereotypes by overachieving. After Lydia dies, James's image of himself shatters, and he begins having an affair with his Chinese research assistant, Louisa. He realizes he always believed Marilyn was too good for him. In the final pages of the novel, James and Marilyn begin healing the wounds of their marriage and seeing each other as actual people rather than symbols (either "different" or "belonging") for the first time.
Marilyn Lee has grown up under the watchful gaze of her traditional, opinionated mother. Marilyn's mother wanted nothing more than for Marilyn to find a successful husband, have a houseful of children, and spend her days caring for her family and home. Marilyn, however, dreamed of becoming a doctor and spent all her time studying math and science. She fell in love with James because, as a Chinese American, he was so different from everyone else. She soon became pregnant and was forced to abandon her studies. Years later, Marilyn would abandon her family and run away to attend college, but the adventure lasted only nine weeks, until Marilyn discovered she was pregnant again. Once she abandons her medical dreams for good, Marilyn focuses all her energy and ambition onto her daughter Lydia. When Lydia dies, Marilyn must once again reconcile her shattered dreams.
Jack Wolff is a mysterious character to most of the Lee family. Nath misinterprets many of his interactions with Jack and believes him to be a cruel bully. James sees Jack as the perfect example of a strong, confident American boy. Lydia sees Jack as a "bad boy" with whom a friendship would annoy Nath. She tries to use Jack to "transform" herself, but Lydia ends up feeling rejected. Jack's secret is that he's in love with Nath and uses Lydia's friendship as a way to learn more about him.