Tyler and Cameron Winklevoss—the brothers who tried and failed to gain control of Facebook after alleging that it had been appropriated from them—have rebounded big-time.

The Winklevoss twins own one of the largest portfolios of Bitcoin in the world—and recent surges in the digital currency’s value have put the value of that portfolio at over $1 billion. That’s an impressive return on an $11 million investment just four years ago.

The brothers have reportedly not sold a single one of their Bitcoins, sitting on them and watching them accrue value. And it’s been a stunning thing to witness: when the Winklevoss’s invested in Bitcoins, the currency was trading at just $120. As of Monday morning, a single Bitcoin’s value was $11,247, according to Coindesk.

That investment money came from the $65 million the brothers’ won in a lawsuit against Facebook in 2011. The brothers had claimed Mark Zuckerberg stole their idea for a social network while all three were undergraduate students at Harvard, a fight that was featured in the film aptly titled The Social Network.

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SOURCE: Fortune, Chris Morris