The fashion designer, who was married to David's brother, Andy, was found dead in New York City on Tuesday.
David Spade is remembering his late sister-in-law.
The 53-year-old actor took to Instagram on Tuesday to mourn the death of Kate Spade, who was found dead hours earlier in her New York City apartment. David and Kate -- who married David's brother, Andy, in 1994 -- sweetly smile at each other in the blurry photo.
"Fuzzy picture but I love it. Kate and I during Christmas family photos. We had so much fun that day," David captioned the shot. "She was so sharp and quick on her feet. She could make me laugh so hard."
"I still cant believe it," he continued. "It's a rough world out there people, try to hang on."
Shortly after, on Twitter, Spade shared another sweet memory, writing, "Katy at my book signing. I love this pic of her. So pretty. I don't think everyone knew how f**king funny she was... It's a rough world out there people. Try to hang on."
The NYPD confirmed to ET that Kate, 55, was found dead in her Manhattan apartment on Tuesday and her body was discovered by an individual who was employed by her. The cause of death is an apparent suicide at this time.
Kate, who is also aunt to Marvelous Mrs. Maisel star Rachel Brosnahan, is survived by her teenage daughter, Frances, and her husband, Andy.
"We loved Kate dearly and will miss her terribly," Kate's family said in a statement to to the New York Daily News. "We would ask that our privacy be respected as we grieve during this very difficult time."
ET has reached out to David's rep for comment.
If you or someone you know needs help, please call the National Suicide Prevention Lifeline at 1-800-273-TALK (8255).
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