"We are heartbroken to announce the passing of our brother and son, Nicholas Brendon. He died in his sleep of natural causes," the family wrote in a statement.
The American actor broke through in the 1990s with the role of Xander Harris on the classic television series "Buffy the Vampire Slayer."
Brendon had previously suffered a heart attack and had a congenital heart defect. He had been open about suffering from depression and had been arrested by police on several occasions on suspicion of crimes.
"He was receiving medication and treatment to manage his diagnosis and was optimistic about the future at the time of his passing," the family wrote.
Nicholas Brendon was 54 years old.
