John Travolta is "devastated" after losing his wife Kelly Preston, who passed away on Sunday after a two-year battle with breast cancer.

A source told Us Weekly that Kelly Preston's family is finding it difficult to deal with her demise as the 57-year-old was the "rock, the heart, and soul who kept the family united."

The source also said that Preston and John Travolta "were true partners," and the "Grease" star has been left "devastated" after losing his wife of 19 years. The couple who tied the knot in 1991 after years of dating, welcomed three children together, but their second child and first son, Jett, died after suffering a seizure at the age of 16, in January 2009.

While announcing the demise of his wife in an Instagram post, Travolta stated that he will be taking some time to be there for their two children- 20-year-old daughter Ella, and nine-year-old son Benjamin. The Us Weekly source said that the two children are also beside themselves after losing their mother.

"Ella and Kelly were best friends and inseparable, and of course Benjamin worshiped his mom," the insider said. The source added that the family has a rough road ahead of them, but "they're being strong. However, they still "can't imagine life without her."

Kelly's battle with breast cancer was kept private throughout the last two years. Her husband revealed the diagnosis in a tribute post for Kelly on Monday, writing: "She fought a courageous fight with the love and support of so many."

"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," the 66-year-old further wrote.

The actor couple had starred together in "Battlefield Earth" in 2000, and "Gotti" in 2018, which also marked Kelly's final screen credit.

Meanwhile, tributes poured in for Kelly from all across the film industry. Olivia Newton-John, Travolta's co-star in 1978 Hollywood classic "Grease," shared a throwback picture of herself with Kelly on her social media accounts.

"@therealkellypreston was a radiant, warm and gentle spirit - a loving, devoted wife, mother and sweet friend. My heart breaks for John, Ella and Ben. No words can express my sorrow for her family. Kelly's light shines on in her beautiful children," wrote Olivia, who herself had a rough battle with breast cancer which continues to this date.

John Travolta and Kelly Preston.
John Travolta and Kelly Preston.

The 71-year-old was first diagnosed with breast in 1992, which was followed by the diagnosis of cancer in her shoulder in 2013. In 2018, the actress revealed she has been diagnosed with cancer for the third time as her stage 4 breast cancer had spread to her back with a tumor at the base of her spine.