(18 May 1991 - present) (2 children)
On 18 May 1991, Castle married former Japan Airlines air hostess Sophia, whom he had met in Tokyo whilst competing in the Japan Open tennis tournament. The couple have two children: Georgina (1994) and Claudia (1996). Georgina sang for the Great Ormond Street Hospital charity at the Inter Continental Hotel in May 2008, and gained considerable attention from press and record companies. Both children are sports scholars at their schools. On 11 August 2009, Castle challenged Health Secretary Andy Burnham during an interview on GMTV, after news reports had cast doubts on the effectiveness of Tamiflu against the swine flu virus. He said: "I can tell you that my child — who was not diagnosed at all — she had asthma, she took Tamiflu and almost died." He is the great-great grandchild of Annie Besant, a prominent British socialist, Theosophist, women's rights activist, writer, orator and supporter of Irish and Indian self-rule.