TOKYO (AFP) - The mother of former Japanese prime minister Yukio Hatoyama, who was dubbed the "Godmother" of a powerful political and business clan, has died, her younger son's office said Tuesday. She was 90.

Ms Yasuko Hatoyama, the daughter of the founder of tyremaker Bridgestone, married into the Hatoyamas, a powerful political family sometimes dubbed "Japan's Kennedys". She married former foreign minister Iichiro Hatoyama, whose father was a prime minister shortly after World War II.

Her sons both became parliamentarians, with the older, Yukio, becoming prime minister in 2009 as the leader of the centre-left Democratic Party of Japan.

He stepped down after less than nine months amid widespread complaints about his dithering and his weak leadership style.

Ms Yasuko Hatoyama was for a long time seen as the real power in the family, which led to her being dubbed the "Godmother", a play on the 1972 US mafia movie "The Godfather".

She continued to be a controversial figure in Japanese politics, allegedly gifting hundreds of millions of yen to her sons in Bridgestone shares and in cash.

This was probed as a possible illegal political donation, but no charges were ever laid against her.