The news of Elvis Presley’s grandson, Benjamin Keough’s tragic passing shocked the world.

An outpouring of grief for the 27-year-old son of Benjamin Keough and Lisa Marie Presley has since followed the heartbreaking passing.

Among those who shared their condolences was the Duchess of York, Sarah Ferguson.

Fergie took to Instagram to post a photo of herself with Lisa Marie, as she spoke of the tragic loss as well as her special bond with the star.

“You stayed with me in my darkest moment and I am here in Yours .. love you my sister Lisa Marie .. wherever, whatever I am with you, in all steadfastness,” Sarah wrote.

“Dearest Lisa Marie, Finley, Harper and Riley. You have a family here and I love my sissy .. love you to your heart and will never stop loving my sissy.”

While the friendship may have surprised a few people, the pair have been close for many years. In fact, both their daughters, Princess Beatrice and Riley Keough have been spotted out together, too.

The two families have become intertwined with their friendships spanning two generations.

It is believed Lisa Marie and Fergie initially met on a visit to the U.S.

“They have become very close,” a source told New Zealand's Women's Weekly.

“It may seem an odd combination but they get on very well and have lots in common. Sarah invited her to Bea's birthday. She came with her children and partner.”

This article originally appeared on Over60.