Yamaguchi and his ex-wife who is 5 years younger than him and used to be model, met in October 1999 during a friend's steamboat party and dated for 8 years before getting married on 8 March 2008. On the same night during a TOKIO concert at Nippon Budokan, Yamaguchi dropped a bombshell by announcing his marriage and his wife's pregnancy to the 13,000 fans there. Their elder son was born in May the same year while their second son was born in September 2010. Yamaguchi was the first TOKIO member to get married and ironically, also the first to get divorced.
Sources: Nikkansports / Yomiuri Hochi / Sponichi