I don't know about 7 children, but four of them were as follows: Tokugawa Iemitsu, Tokugawa Tadanaga, Sen hime and Kazuko hime. Only Oeyo is listed as wife, that I could find. This information and more is from Wikipedia!?
http://en.wikipedia.org/wiki/Go-Mizunoo
Caveat emptor,
Henry Soszynski

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: Tokugawa no Masako , empress of Emperor Go
: Mizunoo, was daughter of Tokugawa no
: Hidetada and Asai no Tatsuko (Oeyo).
: She was their 7th child, born Nov 23, 1607.
: Who the other 6th? did Hidetada have other
: children beside those 7?
: Masako married in 1620 Emperor Go Mizunoo;
: she gave him 8 children. Who where they?
: Emperor Go Mizunoo had children by 6 other
: wives: Yotsutsuji no Oyotsu; Kushige no
: Takako ;are there any information about
: them, and about their children?
: