The couple's son Jett died at age 16 in January 2009 after suffering a seizure at the family's holiday house in the Bahamas.
After Preston's death, a source told the magazine that the family is trying to "pick up the pieces" left behind by the loss of their "rock" and "the heart and soul who kept the family united".
News of her shock death was confirmed last month, with a family representative releasing a statement to People magazine.
"On the morning of July 12, 2020, Kelly Preston, adored wife and mother, passed away following a two-year battle with breast cancer," it read.
"Choosing to keep her fight private, she had been undergoing medical treatment for some time, supported by her closest family and friends.
"She was a bright, beautiful and loving soul who cared deeply about others and who brought life to everything she touched. Her family asks for your understanding of their need for privacy at this time."
Shortly afterwards, Travolta led tributes to his late wife on Instagram with a heartbreaking post.
"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," he posted.
"She fought a courageous fight with the love and support of so many. My family and I will forever be grateful to her doctors and nurses at MD Anderson Cancer Center, all the medical centres that have helped, as well as her many friends and loved ones who have been by her side. 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."
Daughter Ella followed with a touching message to her late mum, thanking her for being there for her "no matter what".
"I have never met anyone as courageous, strong, beautiful and loving as you," she wrote to her 166,000 Instagram followers.
"Anyone who is lucky enough to have known you or to have ever been in your presence will agree that you have a glow and a light that never ceases to shine and that makes anyone around you feel instantly happy.
"Thank you for being there for me no matter what. Thank you for your love. Thank you for your help and thank you for making this world a better place. You have made life so beautiful and I know you will continue to do so always. I love you so much mama."
Preston was born Kelly Kamalelehua Smith on October 13, 1962, in Hawaii. She briefly lived in Australia as a teenager and attended Pembroke School in Adelaide.
She launched her acting career in 1985 with her first major movie role in Mischief after several minor roles in television shows, including For Love and Honor.
Preston went on to star in films such as SpaceCamp (1986), Twins (1988), Jerry Maguire (1996) and For Love of the Game (1999).
Preston's final film role was in the 2018 film Gotti in which she played Victoria Gotti, the wife of Mafia boss John Gotti, who was portrayed on screen by Travolta.