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7 year oldPolice are treating the deaths of Barry Sherman, 75, and his wife Honey, whose bodies were found in their Toronto home on Friday, as "suspicious" but say no suspects are being sought.
Canadian media, citing police sources, say the case is being investigated as a possible murder-suicide.
But a family statement said no-one close to the couple believed this.
"Our parents shared an enthusiasm for life and commitment to their family and community totally inconsistent with the rumours regrettably circulated in the media as to the circumstances surrounding their deaths," it read.
The statement went on to call for a "thorough, intensive and objective criminal investigation" and for the media to stop reporting on the cause of the deaths until the investigation was finished.
The couple's bodies were found by their estate agent, who had been trying to help sell the property. There was no sign of forced entry.
Police say they are awaiting the results of post-mortem exams before deciding on their next steps.
Several Canadian newspapers say they were told investigators were working on the assumption Mr Sherman had killed his wife before killing himself.
Tributes have meanwhile been pouring in for the pair, with Canadian Prime Minister Justin Trudeau tweeting "condolences to their family & friends, and to everyone touched by their vision & spirit".
One of Canada's richest men, Mr Sherman was the founder and chairman of pharmaceutical giant Apotex, which sells generic medicines around the world.
A gifted student, Mr Sherman entered the trade through his uncle's Empire Laboratories, working for him while still at university before buying the company when his uncle died.
He went on to sell Empire, creating Apotex, the company that made him a billionaire and which now employs more than 10,000 people.
But he became embroiled in a family dispute, with his uncle's children seeking a stake in Apotex, arguing they had been cheated. A judge threw out their claim earlier this year.
He also faced an investigation as to whether he had improperly held a fundraiser for Justin Trudeau before he became prime minister.
Mrs Sherman was a board member for several hospitals, charities and Jewish organisations. The couple had four children and have given millions to charity.