Engaged to Jane Loughman on December 25, 2006.

Wedding to Jane Loughman set for June 2008.

Originally appeared as Dr. Rodney McKay', a one-off guest star in "Stargate SG-1" (1997) episode "48 Hours" . He was then invited back for the Season Six premiere "Redemption, Parts 1 & 2" the following season. When the shows creators were casting the spin-off series "Stargate: Atlantis" (2004), he was originally called in to read for a different role. However, he returned to the "Stargate franchise" as McKay, only this time, he was a series lead in the smash hit, "Stargate: Atlantis" (2004).

With his girlfriend Jane Loughman he adopted a dog from a local animal shelter which was scheduled for being euthanized. The Rottweiler-Terrier mix is now called Mars, and is one of the stars of David and Jane's new comedy feature film called A Dog's Breakfast (2007).

Brother of Kate Hewlett

Used to run an Internet media company, Darkyl, with his sister in Toronto.

His fiancée, Jane Loughman, had a son named Sebastian Flynn Loughman Hewlett, on October 6th, 2007.

He is a big fan of "Doctor Who" (1963). His favourite Doctor was Tom Baker.

Went to high school with director Vincenzo Natali and has appeared in three of his films. Had worked with Andrew Miller and suggested him to Natali for Cube (1997).