A Quebec billionaire at the centre of a messy and public airing of his 10-year relationship with a young Brazilian summed up yesterday why he never married her, despite having three children together.

"It's not my cup of tea," the man, who can't be identified under provincial law, told a packed Quebec Superior Court room. His former common-law wife has launched a constitutional challenge to Quebec's unique-in-Canada family law to receive financial support, in a case that could affect the rights of the one million common-law couples in the province.

"I just wish I wasn't in the middle of it," the man said. "I'm disappointed that what was supposed to be a constitutional debate has evolved into an airing of our dirty laundry."

In Quebec, couples living common-law have to pay only child support and are under no obligation to provide support to the spouse, or to divide assets once the union ends.