Kelly Preston was the ''rock and heart and soul'' of her family.

The 57-year-old actress died at the weekend after a secret two-year battle with breast cancer and her husband John Travolta and children Ella, 20 and Benjamin, nine, have been left devastated by her death.

A source told Us Weekly that Kelly was ''the rock, the heart and soul who kept the family united. Kelly and John were true partners''.

The insider added: ''Ella and Kelly were best friends and inseparable, and of course Benjamin worshiped his mom.''

Kelly and John, 66, also had a son Jett, who died in 2009 at the age of 16 after suffering a seizure.

John announced Kelly's death on Instagram by writing: ''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. 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 centers 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. All my love, JT.(sic)''

And Ella shared a touching tribute to her ''courageous, strong, beautiful and loving'' mom.

She wrote: ''I have never met anyone as courageous, strong, beautiful and loving as you.

''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.[heart emoji]''