From PEOPLE Magazine Click to enlarge
Growing up in the Zuckerberg home, Randi, the oldest of four, "was our ringleader," says sister Donna. "She used to convince us to let her direct and film us singing show tunes, fighting duels or pretending we were Titanic survivors. One day she was our editor-in-chief and we owed her articles for a family newsletter." Flash forward and Randi ends up working for little brother Mark, the founder of Facebook. She allows that there was little hope of competing with that. "I have a sibling who has literally changed the way we communicate," says Zuckerberg, 30.

But now the ringleader is ready to run her own circus. After six years in marketing at Facebook, she left in 2011 with generous stock options and founded Zuckerberg Media to produce what she lovingly calls "geek culture." First up: a reality show for Bravo, Start-Ups: Silicon Valley, about six entrepreneurs vying to launch the next must-have app. Critics were rough (Wired snipped that the players "behave like fools and drink like fish"), but Zuckerberg defends her choices: "Showing coding for 10 hours is not going to keep people tuned in."

For this mom of toddler son Asher (her husband is Brent Tworetzky of Chegg.com, a textbook-rental site), partying is reduced to a monthly staff karaoke night. "Son of a Preacher Man" is "Randi's big song," reveals VP Bradley Lautenbach. Otherwise it's barbecues at home. "We're a close-knit family," says Zuckerberg, who sees room to break out professionally. "I'm trying to create my own path."