Mathieu Bissonnette is the identical twin brother of Alexandre Bissonnette, the perpetrator of the 2017 Quebec City mosque shooting. Born and raised in Quebec City, Canada, he grew up in a middle-class family alongside his brother in the Beauport neighborhood. The brothers were close during their upbringing, attending the same schools and sharing similar interests in video games and online activities. Prior to the January 29, 2017 shooting at the Islamic Cultural Centre of Quebec City, Mathieu and Alexandre shared an apartment in the Cap-Rouge area of Quebec City, where they lived as young adults navigating post-secondary education and entry-level employment. Mathieu was not involved in the mosque shooting, which resulted in six deaths and five injuries. Following the attack, he cooperated fully with authorities, providing information during the police investigation into his brother's motives and background. He was questioned extensively but was never charged or implicated in any wrongdoing. Reports indicate he was shocked by the events and distanced himself from his brother's far-right ideologies, which had been influenced by online extremism. Since the shooting, Mathieu has maintained a low public profile, with limited information available about his current activities or residence. He is believed to have continued his life in Quebec, possibly pursuing studies or work in a non-public capacity. The tragedy deeply affected the Bissonnette family, and Mathieu has largely avoided media attention in the years following the event.