Robert James Fischer (March 9, 1943 - January 17, 2008) was an American chess grandmaster and the eleventh World Chess Champion. Many consider him to be the greatest chess player of all time. Bobby Fischer showed great skill in chess from an early age; at 13, he won a brilliancy known as "The Game of the Century". At age 14, he became the US Chess Champion, and at 15, he became both the youngest grandmaster up to that time and the youngest candidate for the World Championship.

Bobby Fischer was born at Michael Reese Hospital in Chicago, Illinois, on March 9, 1943. His birth certificate listed his father as Hans-Gerhardt Fischer, also known as Gerardo Liebscher, a German biophysicist. His mother, Regina Wender Fischer, was a US citizen, born in Switzerland; her parents were Polish Jews. Raised in St. Louis, Missouri, Regina became a teacher, registered nurse, and later a physician.  After graduating from college in her teens, Regina traveled to Germany to visit her brother. It was there she met geneticist and future Nobel Prize winner Hermann Joseph Muller, who persuaded her to move to Moscow to study medicine. She enrolled at I.M. Sechenov First Moscow State Medical University, where she met Hans-Gerhardt, whom she married in November 1933. In 1938, Hans-Gerhardt and Regina had a daughter, Joan Fischer. The reemergence of anti-Semitism under Stalin prompted Regina to go with Joan to Paris, where Regina became an English teacher. The threat of a German invasion led her and Joan to go to the United States in 1939. Hans-Gerhardt attempted to follow the pair but, at that time, his German citizenship barred him from entering the United States. Regina and Hans-Gerhardt had separated in Moscow, although they did not officially divorce until 1945.  At the time of her son's birth, Regina was "homeless" and shuttled to different jobs and schools around the country to support her family. She engaged in political activism, and raised both Bobby and Joan as a single parent.  In 1949, the family moved to Brooklyn, New York City, where she studied for her master's degree in nursing and subsequently began working in that field.

Using a quote from the above article, answer the following question: Did he have any siblings?
Joan Fischer.