Well-known boxing brothers Koki and Daiki Kameda failed to declare some ¥100 million in combined taxable income over several years to 2007, sources said Friday.

The brothers, who apparently filed a return with the Tokyo Regional Taxation Bureau for back taxes amounting to millions of yen, were both declaring self-employed income but failed to attach receipts to many of the expenses they booked. Authorities thus disallowed the deductions, the sources said.

Their Tokyo-based management company, Kameda Promotion, which is run by their father, Shiro, 44, also failed to declare about ¥10 million in income, the sources said.

Koki, 22, the oldest of the three Kameda boxing brothers, is a former WBA light flyweight champion, while Daiki, 20, the second son, is a flyweight boxer who failed to claim the WBA title in early October.