Brown-Forman saw the acquisition as an opportunity to broaden and strengthen its existing RTD portfolio footprint in New Zealand, Australia, and potentially beyond.
Part Time Rangers currently offers a range of six RTD products including Lime Vodka, Passionfruit Apple Vodka, Apple Lime Rum, Strawberry Raspberry Gin, Ginger Lime Whiskey, and Apple Lemon Gin.
The company says it supports local and global wildlife and ecosystem preservation initiatives.
The Deane brothers will remain with Part Time Rangers and the mission to support wildlife conservation and environmental preservation projects will continue, the company said in a statement.
"Our growth since then has exceeded our wildest dreams, and the sale of the business to Brown-Forman will now allow our mission to grow," the brothers said in a statement.
"The decision to sell was not easy and one that we only took after assuring ourselves that Brown-Forman would be a strong custodian for the Part Time Rangers brand and community," they said.
"This process took many months including visiting Brown-Forman in Kentucky to be sure that they understood, valued and supported the mission and direction of Part Time Rangers," they said.
Recent donations included $20,000 to the Rhinos Without Borders project in Botswana, according to its website.
The company also funded 10 Big Life Foundation rangers for two months protecting big-tusk elephants in Africa.
Part Time Rangers was advised by Toby Groser at Montarne Partners and Scott Moran at Duncan Cotterill.
Details of the transaction were scarce but Groser told the Herald: "It's an incredible story of two young guys having an idea and getting up the guts to do it.
"It's a real success story for young people outside the field of tech," he said.
New York Stock Exchange-listed Brown-Forman is a 150-year-old global spirits company based in Kentucky.
Alongside Jack Daniel's, the company has the Finlandia, Woodford Reserve and el Jimador brands in its portfolio.