Dave Goldberg, head of survey company SurveyMonkey and husband of Facebook chief operating officer Sheryl Sandberg, has died aged 47.
His death was confirmed by SurveyMonkey. The company did not disclose the cause of death.
Mr Goldberg and Sheryl Sandberg had two children. Mark Zuckerberg, chief executive of Facebook and a friend of the family, said Mr Goldberg's death occurred while on holiday abroad with Sandberg.
Mr Goldberg's brother Robert spoke of the family's "incredible shock and sadness" at the death.
In a facebook post he said: "In this time of sorrow, we mourn his passing and remember what an amazing husband, father, brother, son and friend he was.
"No words can express the depth of loss we feel, but we want his children to learn how much he meant to all of you.
"In lieu of donations, we want to celebrate his life in a manner that respects the family’s privacy as they cope with this tragic, life changing event: Sheryl, their children, and our family would be grateful if people would post their memories and pictures of Dave to his Facebook profile."
Dave Goldberg's facebook page has been retitled 'Remembering Dave Goldberg'.
In his last facebook post, Dave Goldberg spoke of his pride in Sheryl Sandberg's achievements, saying: "I am really very lucky to have such an incredible partner in my life." They had been married 11 years.
In her book 'Lean In', Sandberg said Goldberg supported her career decisions and shared equally in raising their young children.
In a statement, SurveyMonkey said: “Dave’s genius, courage and leadership were overshadowed only by his compassion, friendship and heart. Our sympathy goes out to them and to all who were touched by this extraordinary man. We are all heartbroken.”