Prime Minister Junichiro Koizumi visited the graves of his father and grandfather in Yokohama on Saturday, the first day of his summer vacation.
Koizumi's grandfather, Matajiro, was posts minister and vice speaker of the House of Representatives. His father, Junya, was head of the Defense Agency.
Joined by his older sister Nobuko -- who is also his secretary -- Koizumi cleaned the graves with water, burned incense sticks and prayed, as is Japanese custom.
Saturday was the first day of the traditional Bon midsummer holiday, when Japanese traditionally visit their relatives' graves and offer prayers.
Koizumi is on holiday until Aug. 22, the prime minister's office said earlier.