Hosokawa's wife returned to the U.S. in anticipation of the birth of their first child. Hosokawa did not see his son, Michael, until the baby was 14 months old. The family lived in Seattle in 1941, just before the Japanese attack on Pearl Harbor. Soon after the attack, President Franklin D. Roosevelt signed Executive Order 9066. As a result, Bill Hosokawa, his wife, and the couple's infant son were among 120,000 Japanese Americans on the West Coast who were sent to Japanese internment camps during World War II.