Franklin Ramón Chang Díaz was born in San José, Costa Rica on April 5, 1950 to a Costa Rican father of Chinese descent, Ramón Ángel Chang Morales, an oil worker whose own father fled China during the Boxer Rebellion. His mother is also Costa Rican, María Eugenia Díaz Romero. One of six children, he has a younger sister, Sonia Rosa (born December 1952) and his mother, brothers and sisters live in Portland. His elder daughters are Jean Elizabeth (born December 1973) and Sonia Rosa (born March 1978) who is a member of the Massachusetts Senate. He married in the United States, on 17 December 1984, interior designer Dr. Peggy Marguerite Doncaster (née Stafford, of Alexandria, Louisiana), the founder of Stafford Tile and Stone, and his younger daughters are Lidia Aurora (born March 1988) and Miranda Karina (July 1995), both born in Houston, Texas.