Keir was born and raised in Sydney, Australia. With an Australian father and a British mother, Keir was born into dual citizenship. At the age of 8, his family, including his 18 month older brother Patrick, moved to Harvard, MA. Now he has tri-citizenship! Keir attended Bromfield High school in Harvard, MA and started acting in as many school plays as he could get his hands on.

After graduating, he was accepted and attended The Hartt School in Hartford, CT. He was part of the first class of the newly-created four year classical theatre acting conservatory. The Hartt School of Theatre was established by Malcolm Morrison and Alan Rust (N.C.S.A. North Carolina School of the Arts).

At The Hartt School Keir performed in numerous plays including Three Sisters, Lysistrata, Twelfth Night, Philadelphia Here I Come, and played Romeo in Romeo and Juliet. After Graduation, he was accepted into the prestigious Hartford Stage Co. Regional Theatre under the tutelage of Michael Wilson. There he appeared in Macbeth and A Christmas Carol.

Soon after, Keir packed up his car and moved to Los Angeles. His break came after performing a 3-person U.S. premiere of a German play, The Man Who Never Yet Saw Woman's Nakedness, at The Odyssey Theatre in West LA. After a slew of student and independent films, he landed his first big role as Christopher Walken's son (Todd Cleary) in New Line's Wedding Crashers. Since Crashers, Keir has been working consistently in various film and television roles.

He lives in Los Angeles. His brother lives in Los Angeles. His father lives in Texas. And his mother lives in Scotland.