Younger half-brother of actor Sean Astin.
Son of Patty Duke and John Astin.
Was accepted to Johns Hopkins University, but did not enroll.
Brother-in-law of producer Christine Astin.
Uncle of actress Ali Astin, Elizabeth Louise Astin and Isabella Louise Astin.
Dominic Monaghan was his roommate for a while. Mackenzie later made a guest appearance on Dominic's TV show, Lost (2004).
Nephew of Ray Duke.
Has three other half brothers: David, Allen and Tom
Lost the top part of his right ear in a car accident.
Writes, makes and stars in his own Super 8 films.
He is of English, Irish, Scottish, and German descent.
He and his brother, Sean Astin, both guest-starred in Season 9 of NCIS (2003). Mackenzie was in the episode, NCIS: Life Before His Eyes (2012), and Sean was in NCIS: The Tell (2012).