Demi Moore is mourning her friend.
In the pic, Willis, 65, holds a small child while Preston playfully nibbles on the baby's feet. All four adults wear smiles in the photo.
"The world has lost one of the most beautiful, kind, generous, tender-loving souls that has graced this earth," Moore said in the caption. "Rest easy @therealkellypreston, we will miss you."
Aside from Travolta, 66, Preston is survived by two children: Ella, 20, and Benjamin, 9. The couple also had a son, Jett, who died in 2009 at the age of 16.
The tragic news of Preston's passing was confirmed on Sunday in an Instagram post from Travolta, who shared a picture of his late wife alongside a loving message in tribute.
"It is with a very heavy heart that I inform you that my beautiful wife Kelly has lost her two-year battle with breast cancer," the "Grease" star revealed. "She fought a courageous fight with the love and support of so many."
He continued: "Kelly’s love and life will always be remembered. I will be taking some time to be there for my children who have lost their mother, so forgive me in advance if you don’t hear from us for a while. But please know that I will feel your outpouring of love in the weeks and months ahead as we heal."
Travolta and Preston married in 1991. The actor starred alongside Willis in "Pulp Fiction" while Willis also lent his voice to the "Look Who's Talking" franchise, which starred Travolta.