The children of late actor Christopher Reeve have paid tribute to Robin Williams, who was their dad's close friend and college roommate.
Reeve and Williams struck up a friendship in the 1970s while attending New York's prestigious Julliard School, where the aspiring actors became roommates.
They remained close after college and made a vow to one another, promising that the first person to make it big in Hollywood would take care of the other.
The Reeve family have thanked Williams for his "simple, steadfast frienship" in a statement published on People.com.
"For Robin, our dad was 'Brother Reeve'. Robin was a light in our family for as long as we can remember. He and Dad made each other laugh, and they stood by each other to the end. Our hearts ache for his family," the statement reads.
"The Reeve family, like many, will remember Robin for the humour, energy and brightness he brought into our lives through the screen. We will cherish him, though, for the quiet and unwavering support he showed our family through the hardest times. The world knew Robin as a comedic titan, but to our family, he was simply one of our Dad's dearest friends. From the moment they were classmates at Julliard, their friendship transformed into a brotherhood that was built on a mutual admiration for the theatre, the arts and, most importantly, laughter."
Williams stood by Reeve when the Superman star was left paralysed following a horse riding accident in 1995.
The Mrs Doubtfire actor reportedly helped to pay for Reeve's medical treatment and lifted the quadriplegic's spirits as he prepared to undergo life-saving surgery by bursting into the operating room, pretending to be an eccentric Russian surgeon ready to perform a rectal exam on him.
Williams, 63, died from an apparent suicide on Monday, 10 years after Reeve suffered a fatal heart attack in 2004.
In 2005, Williams dedicated his Cecil B. Demille Award at the Golden Globes to his late friend and was also a key supporter of the Christopher & Dana Reeve Foundation, a charity set up by the Reeve family following the death of Christopher's wife, Dana, in 2006.
The organisation aims to raise funds to find treatments and cures for paralysis caused by spinal cord injury.
The charity added their words of condolence late on Monday, in a message that reads: "While the world knew Robin Williams as an Oscar-winning actor, we knew a different side to the man whose smile was as big as his heart.
"While our hearts ache with the loss of our friend, it is unlikely Robin would want us to mourn his passing with silence, but to celebrate his life through laughter.
"Together, let's remember Robin for the man who made the world laugh."
* Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14 or the Suicide Call Back Service 1300 659 467.