Courteney Cox speaks for the first time about the death of her sister-in-law Alexis Arquette.

On Monday, the world learned of actress Alexis Arquette’s passing.

The 47-year-old suffered a long battle with a mystery illness, and died in the company of her famous siblings and loved ones. In her final moments her ears were filled with her favourite song – David Bowie’s Starman. 

When she went, friends and family erupted into a cheer upon her request.

In the wake of her death, former sister-in-law and Friends alum Courteney Cox – who was married to David Arquette from 1999 to 2003 – paid tribute to Arquette.

“My heart goes out to anyone who was lucky enough to know Alexis,” Cox wrote in a tweet on Monday afternoon.

“We will love you and miss you forever.”

Arquette was a staunch advocate of transgender rights, having herself transitioned in 2001.

“Our brother Robert, who became our brother Alexis, who became our sister Alexis, who became our brother Alexis, passed this morning September 11, at 12:32 am,” brother Richmond wrote shortly after her passing on Facebook.

"He was surrounded by all of his brothers and sisters, one of his nieces and several other loved ones. We were playing music for him and he passed during David Bowie's Starman. As per his wishes, we cheered at the moment that he transitioned to another dimension."

While the cause of Alexis' death was not specified, Richmond expressed the family's gratitude that her passing was "swift and painless", writing, "He died as he lived, on his own terms."