In 2005, Catherine Cook came up with a golden idea: digitizing yearbooks. She was 15 years old.
New to Montgomery High School in Skillman, N.J., Cook and her then 16-year-old brother, David Cook, were faced with the daunting task of making new friends in a new school.
"[We] thought that our existing yearbook was a terrible tool for meeting new people," Catherine Cook said in an e-mail interview with ABCNews.com.
While flipping through their yearbook one night, the siblings came up with an innovative way of meeting new teens: myYearbook.
"It turned out that meeting new people became the kernel idea [of myYearbook] which we then started to innovate and launch products around," said Geoff Cook, Catherine and David's older brother, who quickly got involved in the project after graduating from Harvard by helping to foot the bill for the start-up.
Six years later, the three Cook siblings are multi-millionaires.
On Wednesday, myYearbook announced its sale to the West Palm Beach, Fla.-based Quepasa Corp. for $100 million of combined stock and cash.
"This whole experience has been a dream, but I don't see myself as a millionaire. I'm still an ordinary girl," said Catherine Cook, who is currently vacationing and attending a cousin's wedding in Costa Rica.
With the sale, the family dream-team is growing up: Geoff Cook, 33, will become COO of the joint companies while his younger brother David, 22, finishes college at University of Colorado.
Catherine Cook, now 21, will remain co-founder of myYearbook as she and her brother enter the elite league of millennial moguls. As a recent graduate of Georgetown University, Catherine Cook now works fulltime at myYearbook.
"I am committed to focus on what we do best -- to make myYearbook.com the number one site to meet new people," she said.
Geoff Cook, who had served as CEO of MyYearbook, said,"I don't view this as an exit or the end. I view it as the end of the beginning."
QuePasa buys myYearbook
Quepasa Corp. owns Quepasa.com, a social network whose users are based primarily in Latin America. John Abbott, CEO of QuePasa, said that the company is "very excited" about the acquisition and hopes to bring the merged companies to a global market.
""We believe myYearbook's proven track record in monetization and engagement will fuel significant future growth," Abbott said in a statement.
When the Cooks launched it in 2005, MyYearbook.com operated like a digital yearbook -- friends could sign each other's "virtual yearbooks," swap photos and share study guides. In just a week after their initial launch, the Cooks managed to attract 400 users to the site.
Six years later, this "social discovery" network has evolved, complete with newly launched real-time social gaming with a live video chat capability.
Combined, myYearbook.com and QuePasa.com will have more than 70 million registered web users, most of whom are in the 13 to 24 age range. According to Abbott, a major potential for growth lies within mobile apps, as 40 percent of myYearbook users access that site via mobile devices.
"Eight months ago we had 140 million page views via the mobile devices. Now we're doing 1 billion," Cook said. "It wouldn't surprise me given the rate of growth for mobile to overtake web."
The site generates 1 billion page views on mobile platforms and 1.2 billion page views on the web each month, according to the company. It has also spread to over 32.7 million members worldwide, managing to stay relevant in a market of failing My Spaces and Friendsters.
Cook attributes the success of the company to its focus on meeting new people, rather than duplicating Facebook's social graph of connecting with old friends and family.
"MyYearbook allows you to meet new people who are near you geographically, or who are a similar age to you, or who like to play the same games as you," Cook said. "There's a lot of richness to meeting new people... It's kind of the anti-facebook in that sense."
Still, the myYearbook app and Quepasa app on Facebook have over 2 million and 28,000 monthly active users respectively. Abbott views that social network as a "great way we can draw an audience to our own applications or site."
"We're really excited about the prospects of taking the mobile applications that Geoff has built and rolling those out in Latin America and then worldwide," Abbott said. "The growth potential on that basis is massive."