"She was actively seeking help and working closely with her doctors to treat her disease, one that takes far too many lives", Andy Spade said in the statement, first published on The New York Times website.
She said: "What I mean is we need to respect one another as much as you do the other people in the office because I can find myself if he's on the phone, opening his door and going, 'Hey, hey, I've got to tell you something. It was a complete shock", he said.
"We were not legally separated, and never even discussed divorce", he adds.
The famed handbag designer told Page Six in January she and her daughter, Frances, 13, jumped up and down when Brosnahan won the Golden Globe for her role in The Marvelous Mrs Maisel.
This morning, "Extra" spoke to her former publicist, Rob Shuter, who said Kate "cared deeply about dignity, decency, kindness" but that "deep down, behind the ideal facade, there was a real sadness about Kate".
She sold her ownership stake in the brand in 2006, and in 2016 she revealed she had taken time away from designing in order to focus on parenthood.
"I think women do want something that's interesting", said Spade in July 2000.
Kate's brother-in-law David Spade, who is Andy's brother, also paid tribute with a holiday photo.
But this morning, a People magazine report included sources claiming that Saffo has not talked to her sister in more than 10 years.
Spade, born Katherine Noel Brosnahan, was found unconscious by her housekeeper, the NYPD said. She launched a new fashion brand in 2007, Frances Valentine after leaving Kate Spade New York.
Designer Kate Spade attends the Tribeca Ball 2011 at the New York Academy of Art on April 4, 2011 in New York City.
Kate Spade's older sister says the designer had refused treatment for mental illness.
Since the news broke, however, a number of theories have emerged surrounding Spade's death.
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