These brothers are now instant millionaires after Zynga bought their Solitaire card games for $42.5 million

Zynga's latest filing with the SEC reveals that it paid $42.5 million for four popular Solitaire smartphone games made by Harpan LLC.

A perfectly normal acquisition, if a little steep. The real twist is that Harpan LLC is owned, operated, and staffed by a pair of brothers - Austin-based Tim Oswald and his Chicago-area brother William.

With one deal, they're both millionaires.

This detail in Zynga's filing was first noted by Seeking Alpha.

Analyst firm App Annie shows that Solitaire, Harpan's flagship app, is currently the number-one card game on the Apple iOS App Store, and bounces in and out of the top 10 games overall. It's an advertising-supported free game that's described in its App Store listing as having "crisp, clear graphics, and a straight forward [sic] layout."

Harpan also makes three additional card games, including Pyramid Solitaire, FreeCell, and Spider Solitaire, all offering a similar aesthetic. All of his games are available for iOS and Android.

Notably, Harpan isn't the Oswalds' only venture - Tim's LinkedIn profile connects him to "Tim O's Studios," a separately-listed developer on the Apple App Store that makes simple apps and games like "Calculator%" and "Guitar Tuner."

In a recent on-stage appearance at a Morgan Stanley event, Zynga CEO Frank Gibeau mentioned Harpan and how it fits in with the company's recent strategy of pursuing social card games supported by advertising.