Dave Goldberg, chief executive officer of SurveyMonkey and husband of Facebook chief operating officer Sheryl Sandberg, died unexpectedly on Friday night, his brother wrote in a Facebook post on Saturday.
"It's with incredible shock and sadness that I'm letting our friends and family know that my amazing brother, Dave Goldberg, beloved husband of Sheryl Sandberg, father of two wonderful children, and son of Paula Goldberg, passed away suddenly last night," Robert Goldberg wrote.
Goldberg was known for his low-key demeanor and the grace and good humor with which he handled being married to one of the nation's most recognisable executives.
In her book "Lean In," Sandberg attributed much of her own success to her marriage to Goldberg, who she said supported her career decisions and shared equally in the work of raising their young children. The two married in 2004.
Tributes to Goldberg poured in over social media from friends and other executives, including Facebook chief Mark Zuckerberg, who called Goldberg "an amazing person."
"Kindest, most generous, loving father, loyal husband, great ceo, & sweetest friend," tweeted Salesforce CEO Marc Benioff. "May his memory be a blessing."
Television and movie writer John Quaintance said on Facebook that Goldberg was the first person to encourage him to write professionally, changing the course of his career.
Goldberg was also the first person Quaintance met who owned a Blackberry device. "I rolled my eyes at the idea that people were ever going to need to read their emails away from the office," he wrote.
Goldberg, 47, joined SurveyMonkey, which helps organisations conduct surveys, in 2009. Valued at $2 billion, SurveyMonkey is backed by Bain Capital Ventures, Google Capital, Tiger Global and others.
"Dave's genius, courage and leadership were overshadowed only by his compassion, friendship and heart," the company said in a statement. "His greatest love was for his family. Our sympathy goes out to them and to all who were touched by this extraordinary man."
The family did not disclose the cause of death.