Announced on February 19th, Facebook's $19 billion acquisition of WhatsApp was a deal sealed between the two company CEOs a few days earlier, though it took years of amicable courtship to reach the accord. Forbes has taken a look at the relationship between WhatsApp's Jan Koum and Facebook's Mark Zuckerberg in the buildup to their momentous agreement. It all started with an email from Zuckerberg in the spring of 2012 and culminated with an accepted takeover offer on the Facebook boss' couch a day after Valentine's Day. The two CEOs reportedly celebrated by opening up a bottle of Johnnie Walker Blue Label and hugging one another.

If the story sounds familiar, that's because Zuckerberg used the same approach to woo Kevin Systrom — he and Systrom agreed the price at which Facebook would buy Instagram over a weekend at Zuckerberg's home. So the strategic approach remains the same, even if the numbers involved have ballooned.