Suddenly, "Who's your daddy?" has become a $1.6 billion-dollar question: That's the amount that European private equity firm Permira paid earlier this week to acquire U.S. genealogical website Ancestry.com—a 40 percent premium over the trading price of Ancestry's stock. Genealogy is hot. The same hobby that once was the preferred pastime of shut-ins, spinsters and confirmed bachelors has become widely popular. "It's no longer a niche," says Tim Sullivan, CEO of Ancestry. He tells ABC News is site now has more than 2 million paid subscribers. Ancestry will report a billion dollars in revenue for 2012.. "There's a broad, mainstream interest in family history," Sullivan says.