The 33-year-old is a former US Marine and is known for his disciplined method acting.
Having starved himself for Martin Scorsese’s Silence, Driver has brought his strict techniques to the latest Star Wars movie.
His The Last Jedi co-star Hamill revealed just how seriously Driver takes playing Kylo Ren.
Speaking with Vanity Fair, the Luke Skywalker star said: “He’s very moody and intense.”
Hamill continued: “I remember saying to Adam, ‘I don’t know how you work, or your technique. But, at some point, you were my nephew.
“‘I probably bounced you on my knee. I probably babysat for you.
“‘There’s that side, and now we’re both estranged from the Skywalker family.
“‘All I’m suggesting is, if you’d like, maybe we could go to lunch, we could get together and hang out.’”
However Driver refused the offer because of his acting methods, which Hamill took in his stride.
Hamill added: “And more power to him.”
Star Wars Episode VIII: The Last Jedi is released in UK cinemas on December 15, 2017.