A CONCUBINE'S existence rendered the registry office marriage between a millionaire and his second wife null and void, a High Court judge held yesterday. But Mr Justice Patrick Chan ruled that the marriage between the late Kwan Kai-ming, a former director of the Tung Wah Group of Hospitals, and Chui Kwok-ying was valid because the couple were also wed according to customary Chinese law. Apart from confirming Ms Chui was Kwan's lawful widow, the judge found that Tao Wai-chun was the businessman's lawful concubine and her four offspring were his legitimatechildren. Kwan died in 1983, aged 80, without making a will. His estate is believed to be worth about $200 million. The probate action arose after Ms Chui and one of her husband's 16 children, Suzanna Kwan Sau-hang, asked the court to clarify the legal position of Ms Tao and her children. But Kwan Chi-on, a son of Kwan's first wife, filed a counter-claim, asking the court to declare Ms Chui was not his father's lawful widow and that Ms Tao and her children were not the legitimate concubine and offspring. The son also filed a third-party action, seeking a declaration that one of his younger brothers, Daniel Kwan Tit-on, was not his late father's natural son. Those actions were unsuccessful. In dismissing his claim, Mr Justice Chan ordered Mr Kwan Chi-on to pay half the costs of the main action to the plaintiffs, Ms Tao and her children, and to Mr Daniel Kwan. The court was told the late Kwan had run successful business ventures in Hong Kong, Manila and Macau. He married Wong Woon-wan in 1923. The first Mrs Kwan died in 1959 and, the following year, Kwan married Ms Chui. She told the court they had made their vows at the Marriage Registry on May 27, 1960. About the same time, they went through some form of marriage ceremony in accordance with traditional Chinese law.