Gadhafi and his wife were in the Tripoli house of his 29-year-old son, Saif al-Arab Gadhafi, when it was hit by at least one missile fired by a NATO warplane, according to Libyan spokesman Moussa Ibrahim.
"The leader himself is in good health," Ibrahim said. "He was not harmed. The wife is also in good health."
"The attack resulted in the martyrdom of brother Saif al-Arab Gadhafi, 29 years old, and three of the leader's grandchildren," Ibrahim said. He described Saif as a student.
The one-story house in a Tripoli residential neighborhood was heavily damaged.
Saif al-Arab Gadhafi was the sixth son of Gadhafi. He had spent much of his time in Germany in recent years.