From WENN.com

Paxton and Kevin Costner play real-life rivals Randall McCoy and William Anderson Hatfield, who lead their clan into a bitter battle over the theft of a pig - despite recently becoming the best of friends as comrades during the U.S. Civil War.

Chaos ensues as growing tensions turn the feud into an all-out war over family honour and justice, and Paxton admits he had such a tough time getting into character, he dug up his old relative's letters in a bid to better understand the mindset of the era.

He tells the New York Times, ""I went down to Pikeville, Kentucky to do a little research. But these were men who didn't leave a written record. I had a book of letters that my great-great-grandfather Elisha Franklin Paxton had written to his wife during the Civil War. He had gone to Yale (University) and died at age 35 at the Battle of Chancellorsville, leading Stonewall's Brigade (a Confederate Army combat unit).

""The mind-set of that time, when every decision you made was based on Christian duty and honour, was a foreign concept to a modern mentality. To really hear someone of their time speaking under duress was helpful to both these characters, who started out like brothers in the Civil War and came out enemies.""