Musk may have five young boys from his first marriage — one set of twins and one set of triplets — but he's already donated much of his $12.9 billion fortune to renewable energy, science and engineering education, and pediatric health.
Gates has been open about his decision not to leave his $84.9 billion fortune to his three children. They will reportedly inherit just a small slice, about $10 million each.
"I definitely think leaving kids massive amounts of money is not a favor to them," he said in a Reddit AMA in February.
He founded the Bill & Melinda Gates Foundation in 1994, and it currently has more than $36 billion in assets. Gates also teamed up with longtime friend Warren Buffett to start a campaign called "The Giving Pledge," which encourages other billionaires to donate at least half of their fortune to charity.
"Warren Buffett personally asked me to write this letter because he said I would be 'setting an example' and 'influencing others' to give. I hope he's right," his letter to the Giving Pledge said in August 2010.
Despite committing the majority of his wealth to charity, he also gave his children Oracle stock when they were still babies (and the company was also young). Now that both the stock and company are worth a lot more, he is reported as to wanting to teach them charitable giving too.
Google CEO Larry Page
Page, on the other hand, has a somewhat unique idea for what he would like to happen to his wealth.
In March, he told Charlie Rose that instead of giving his billions to his two children, he would rather give it to entrepreneurs like Elon Musk, who are coming up with big ideas to change the world.
"[Musk] wants to go to Mars. That’s a worthy goal," he said. "We have a lot of employees at Google who’ve become pretty wealthy. You’re working because you want to change the world and make it better; if the company you work for is worthy of your time, why not your money as well? We just don’t think about that. I’d like for us to help out more than we are."
Omidyar and wife Pam are some of the most generous people in tech, having given away more than $1 billion of the vast fortune they made when eBay went public in 1998.
They signed the Giving Pledge in 2010. Bloomberg estimates their current fortune at $7.8 billion.
"In 2001, I publicly stated that we intend to give away the vast majority of our wealth during our lifetime," the couple said in their pledge letter. "Our view is fairly simple. We have more money than our family will ever need. There’s no need to hold onto it when it can be put to use today, to help solve some of the world’s most intractable problems."
They've also donated eBay shares to the Omidyar Network, their philanthropic investment firm, and are the single biggest private donors in the fight against human trafficking.
Microsoft co-founder Paul Allen
While Paul Allen doesn't have any direct descendants, his family is actively involved in his philanthropy.
"I've planned for many years now that the majority of my estate will be left to continue the work of the Foundation and to fund non-profit scientific research, like the ground breaking work being done at the Allen Institute for Brain Science," he said in his Giving Pledge letter.
Facebook co-founder and CEO Mark Zuckerberg
When Mark Zuckerberg signed the Giving Pledge in 2010, he was only worth $6 billion. Now he's on the books to give away the majority of his $35.9 billion fortune.
Zuckerberg and his wife, Priscilla, have already been active philanthropists. The couple recently gave $75 million in February 2015 to the San Francisco General Hospital, allowing it to add two trauma rooms, three operating rooms and to double the size of its emergency room. He'd also previously donated close to $1 billion in Facebook shares to Silicon Valley Foundation.
Asana CEO Dustin Moskovitz
Facebook's third employee, Dustin Moskovitz, is one of the youngest self-made billionaires to have signed the Giving Pledge.
"As a result of Facebook’s success, I’ve earned financial capital beyond my wildest expectations. Today, I view that reward not as personal wealth, but as a tool with which I hope to bring even more benefit to the world," he said in his letter.
Moskovitz and his partner, former Wall Street Journal reporter Cari Tuna, established Good Ventures as a philanthropic foundation to help distribute his wealth. Moskovitz is also now founder and CEO of Asana, a collaboration software company.
Facebook's Sheryl Sandberg and SurveyMonkey's Dave Goldberg
Sheryl Sandberg, along with her husband Dave Goldberg, signed the Giving Pledge in 2014 to give away half of her wealth. While the couple didn't specify a cause, we have a feeling Sandberg's book "Lean In" might be a pretty strong indication of where their money ends up.
Dave Goldberg tragically died in May after an accident while exercising in Mexico, leaving Sandberg to care for their two children.
Virgin Group founder Richard Branson and his wife Joan Branson
Richard Branson's children are philanthropists in their own right: Their son Sam set up a production company, Sundog Pictures, and their daughter Holly is involved in Big Change Charitable Trust, according to their 2013 Giving Pledge letter.
The Virgin Group founder, and his wife Joan, signed the Giving Pledge in 2013 to give away half their wealth after they realized as a result of several house fires that money does not equate to happiness.
"Stuff really is not what brings happiness. Family, friends, good health and the satisfaction that comes from making a positive difference are what really matters," Branson said in the announcement.
Netflix founder Reed Hastings
Netflix founder and CEO Reed Hastings and his wife Patti Quillin signed the Giving Pledge in 2012 when his net worth was valued only at $280 million. A new entrant on Forbes' World's Billionaires list, Hastings now has a net worth of $1 billion.
Hastings has an interest in education after he served as president of the California Board of Education from 2000 to 2004. The press release announcing their Giving Pledge hinted that it that might be where they put some of their money since they "are active in educational philanthropy and politics with a specific focus on charter schools."
Airbnb CEO and cofounder Brian Chesky
In the last eight years, Airbnb's Brian Chesky has grown the startup from a way to make rent to a company worth $25 billion that could usurp the travel industry altogether.
"If you told my teachers growing up that one of their students would be a signatory of this pledge, I don't think any of them would have picked me. I wouldn't have blamed them. I was a little disruptive in class, to say the least," Cheksy writes in his pledge.
He plans to use his money to help other kids realize their dreams "are not bounded by what they can see in front of them."
Airbnb founder Nathan Blecharczyk and his wife Elizabeth Blecharczyk
At 32, Nathan Blecharczyk is one of the youngest billionaires on the list, thanks to his role as cofounder and CTO of Airbnb. But his youth is something he recognizes could empower him to make bigger changes.
In his giving pledge, Blecharczyk and his wife, Elizabeth, write: "We are humbled to find ourselves at a young age in an extremely privileged place. We recognize that the world has many real challenges and that we are in a unique position to have significant positive impact. We feel a responsibility to share our good fortune, and we pledge to dedicate the majority of our wealth over time to philanthropy."
Airbnb cofounder and Chief Product Officer, Joe Gebbia, pledged to give away the majority of his wealth in May 2016.
"I want to devote my resources to bring the moment of instantiation, when someone who has an idea sees it become real, to as many people as I can. It can unlock the understanding that they can make things happen, that they can shape the world around them. I want to enable as many people as possible, especially in underprivileged communities, to experience this magic firsthand," Gebbia wrote.
AOL cofounder Steve Case
Case helped millions of Americans get online, and now he's donating much of his wealth to developing other technologies.
He founded the Case Foundation in 1997, which focuses on using technology to make philanthropy more effective. He also started an investment firm called Revolution, which invests in startups outside of Silicon Valley, and signed the Giving Pledge.
"We share the view that those to whom much is given, much is expected. We realize we have been given a unique platform and opportunity, and we are committed to doing the best we can with it," he and wife Jean wrote. "We do not believe our assets are 'ours' but rather we try to be the responsible stewards of these resources."
Intuit cofounder Scott Cook and his wife, Signe Otsby
Intuit cofounder Scott Cook and his wife, Signe Otsby, already have a history of giving philanthropy. In 2002, the two endowed the Center for Product Management in the School of Business at their alma mater, the University of Wisconsin-Madison. The two signed the Giving Pledge to help solve world problems not in isolation, but with the support of the community.
"Today's opportunities for social progress are larger than ever before in history. We are lucky to live in a renaissance of entrepreneurship across the fields of human endeavor, and we believe that social entrepreneurs will drive progress on the great challenges of our time," the couple wrote.