Karl has an older brother named Mark. Mark is about 10 years older than Karl, and could be described as a bit of a tearaway. When Karl was first asked about his relationship with his brother commented that he had not seen his brother in 10 years. Also, Karl regularly refers to him as "our kid".
Karl's memories of his brother are not endearing. One particularly unpleasant incident was when, after having several alcoholic beverages, he destroyed Karl's new train set on Christmas Day. This is one of the events that lead to Karl's dislike of Christmas. Other times Mark would bring women into the house while their parents were away. He would barter with Karl to keep silent about it (like letting him ride the tractor through the house). Karl has also alluded to Mark's having been in prison multiple times, as when once Ricky made a joke about a possible nickname for Mark, Karl replied that "he's never out of prison long enough to get a nickname".
Mark is infamous in Pilkington Lore for his exploits in the army. Initially, he got out of fighting in the war in the Falklands because his mother called his commanding officer and begged for him to be kept out of harm's way. Mark's problems in the army worsened when he was discovered to be having an affair with his commanding officer's missus. Eventually he was kicked out for driving a tank down the high street to get a packet of fags.
Mentions on the show
- 16 February 2002 - Karl tells that his brother had girls all over the house as a child, so he had to utilize Feng Shui and sleep on the couch. Karl also makes a passing reference to Mark's prison history.
- 02 March 2002 - Karl tells that his brother would apply for jobs without any skills. He applied to be a mechanic without even picking up a spanner. Karl also compares his brother to Rasputin.
- 09 March 2002 - Karl lets out that his brother got out of the Falklands War because of a note from his mother. Karl also tells that he got kicked out for going for a pack of fags in a tank (and sleeping with the sergeant's wife). Karl hasn't seen his brother in 11-12 years.
- 21 December 2002 - Karl recalls the Christmas that his brother broke his brand new train set.
- 05 July 2003 - Mark moved away from Manchester, but they don't know where he is now.
- Fame Souvenir Program Podcast - "Family Reunion" for the boiler