Yasuko Hatoyama, mother of ex- Prime Minister Yukio Hatoyama, died Monday night of multiple organ failure at a Tokyo hospital, sources close to the former prime minister and his lawmaker brother, Kunio, said. She was 90.

Yasuko was the daughter of Shojiro Ishibashi, the founder of tire maker Bridgestone Corp. She was also the wife of the late Foreign Minister Iichiro Hatoyama, the oldest son of Ichiro Hatoyama, the first president of the Liberal Democratic Party.

Famed for her family's vast wealth, including her shares in Bridgestone, she was known to have supported the political activities of her oldest son, Yukio, and Kunio, an LDP Lower House member who had served in Cabinet posts, including the education and justice portfolios.

In 1996, Yasuko Hatoyama was said to have encouraged the two sons to establish a political party, a suggestion that led to the foundation of the precursor of the Democratic Party of Japan. As DPJ leader, Yukio Hatoyama served as the country's prime minister from September 2009 to June 2010.

While serving as prime minister, one of his campaign funding bodies was accused of having fictitiously listed donors, for which his chief accountant was sacked and convicted. It was later revealed that Yasuko Hatoyama had been providing Yukio Hatoyama with ¥15 million per month for seven to eight years.

According to 2011 income reports and other sources, Yasuko Hatoyama gave ¥4.2 billion in cash, equities and real estate to each son.