"It is with immense grief that we would like to inform our compatriots of the passing away of Prince Alireza Pahlavi," the family website said.
"Like millions of young Iranians, he too was deeply disturbed by all the ills fallen upon his beloved homeland, as well as carrying the burden of losing a father and a sister in his young life. Although he struggled for years to overcome his sorrow, he finally succumbed." The family learned of the death on Tuesday at 2.30 a.m., said spokesman Ahmad Oveyssi.
In June 2001, Pahlavi's sister, Leila Pahlavi, committed suicide.
According to press reports in Britain, the princess had struggled for years against an eating disorder, had never accepted her exile from Iran and suffered periodic bouts of depression.
"For the past few years, Leila was very depressed. Time had not healed her wounds," the princess' mother, Farah Pahlavi, wrote on a remembrance website in 2001.
"Exiled at the age of 9, she never surmounted the death of her father to whom she was particularly close.
"She was never able to forget the injustice and the dramatic conditions of our departure and the erring which was to follow. She could not stand living far from Iran and shared wholeheartedly the suffering of her countrymen."
Alireza Pahlavi was undertaking a postgraduate degree at Harvard University in Cambridge in philology and ancient Iranian studies.
His father was ousted in the 1979 Islamic revolution, and his family moved to live in exile in the United States. The deposed shah died in July 1980 and is buried in Cairo.
