Silicon Valley is beginning to admit it isn’t just for young people anymore.

The valley’s un-family-friendly culture has long been almost a point of pride, with employers openly preferring younger, childless employees who were presumed to be more productive.

“Young people just have simpler lives,” Mark Zuckerberg, Facebook’s co-founder and chief executive, said in 2007, when he was 23. “Simplicity in life allows you to focus on what’s important.”

Recently, though, a growing number of tech executives have been speaking out about the struggle to balance work and family, particularly as Silicon Valley faces pressure to become more diverse.

In an informal poll last month by CB Insights, a private-company data firm, 63 percent of the 4,040 respondents — mostly startup founders who are also parents — said they struggled with balancing their startup and parental duties daily or all the time. Only 10 percent said they never did.

“I know people struggle with this — I certainly do as a parent and founder — but over 60 percent struggling with it every day or all the time even surprised me,” said Anand Sanwal, chief executive of CB Insights.

There are signs the culture could be changing.

On Friday, for example, Zuckerberg sounded a different note when he said he would take two months of paternity leave after his daughter is born. (Facebook offers employees four months of paid parental leave.) On Thursday, Spotify, with headquarters in London and Stockholm and offices worldwide, said it would give full-time employees six months of paid parental leave and one month of transition in which they can work flexible or shorter hours.

Long hours in the office and the expectations of being connected at home are familiar to workers across industries, not just Silicon Valley. Fifty-six percent of parents in dual-income households across the wage spectrum say they find the work-family balance to be difficult and stressful. But tech takes the high-stress, high-stakes American work culture to the extreme.

“The tech industry’s love for scrappy, accessible founders adds to the pressure,” said Glenn Kelman, chief executive of Redfin, the online real estate company. “You’re expected to lead by example, to roll up your sleeves, to know everything going on.”

Tech has been a difficult place for parents in part because there have been so few parents or women among the 20-something startup founders and coders who form large parts of the tech industry.

Many parents who work at small startups report that they were the first person at the company to have a child, and often there was no existing parental leave policy. Even at big companies like Facebook and Amazon, people with children or other outside commitments struggle with things like weekend hackathons or holiday conference calls.

“Being a tech founder is all-consuming; you can never really turn off,” said Clara Shih, founder and chief executive of Hearsay Social, who recently had her first child with her husband, Daniel Chao, also a tech founder and chief executive, of Halo Neuroscience. “You can’t skimp on your family, and you can’t skimp on your startup, so you end up skimping on yourself.

“Many women are written off as not as serious about work and their careers once they have children, so at times I feel like I have to work extra hard to change this perception on behalf of all women in tech,” Shih said.