Over the next decade, Mr. Goldberg and Ms. Sandberg pioneered new ways of capturing information online, had a son and then a daughter, became immensely wealthy, and hashed out their who-does-what-in-this-marriage issues. Mr. Goldberg’s commute from the Bay Area to Los Angeles became a strain, so he relocated, later joking that he “lost the coin flip” of where they would live. He paid the bills, she planned the birthday parties, and both often left their offices at 5:30 so they could eat dinner with their children before resuming work afterward.

Friends in Silicon Valley say they were careful to conduct their careers separately, politely refusing when outsiders would ask one about the other’s work: Ms. Sandberg’s role building Facebook into an information and advertising powerhouse, and Mr. Goldberg at SurveyMonkey, which made polling faster and cheaper. But privately, their work was intertwined. He often began statements to his team with the phrase “Well, Sheryl said” sharing her business advice. He counseled her, too, starting with her salary negotiations with Mark Zuckerberg.

“I wanted Mark to really feel he stretched to get Sheryl, because she was worth it,” Mr. Goldberg explained in a 2013 “60 Minutes” interview, his Minnesota accent and his smile intact as he offered a rare peek of the intersection of marriage and money at the top of corporate life.

While his wife grew increasingly outspoken about women’s advancement, Mr. Goldberg quietly advised the men in the office on family and partnership matters, an associate said. Six out of 16 members of SurveyMonkey’s management team are female, an almost unheard-of ratio among Silicon Valley “unicorns,” or companies valued at over $1 billion.

When Mellody Hobson, a friend and finance executive, wrote a chapter of “Lean In” about women of color for the college edition of the book, Mr. Goldberg gave her feedback on the draft, a clue to his deep involvement. He joked with Ms. Hobson that she was too long-winded, like Ms. Sandberg, but aside from that, he said he loved the chapter, she said in an interview.

By then, Mr. Goldberg was a figure of fascination who inspired a “where can I get one of those?” reaction among many of the women who had read the best seller “Lean In.” Some lamented that Ms. Sandberg’s advice hinged too much on marrying a Dave Goldberg, who was humble enough to plan around his wife, attentive enough to worry about which shoes his young daughter would wear, and rich enough to help pay for the help that made the family’s balancing act manageable.

Now that he is gone, and Ms. Sandberg goes from being half of a celebrated partnership to perhaps the business world’s most prominent single mother, the pages of “Lean In” carry a new sting of loss.