Matthew has a close relationship with his father. Being the curious inventor Henry was, he had a tendency of endangering himself with his experiments. Matthew took it upon himself to look after him.
Matthew unwillingly attended the Shadowhunter Academy in 1899, where he became considerably popular among the students. Wanting instead to return home to look after his eccentric father, Matthew took every opportunity to discredit himself to get expelled—an unlikely idea given his mother's position as Consul. At the Academy, he was friends mostly with Christopher and Thomas Lightwood and had an initially complicated relationship with James. One morning, he and James finally had a conversation about their situation and realized that they were being rude to each other for no reason. The pair since became very close friends, despite the revelation that James had the ability to turn into a shadow.
When James was expelled, for an incident, started by Alastair Carstairs, that led to a student's death, James was blamed and expelled. Matthew had a confrontation with Alastair on the day of James's departure from the Academy. Matthew intended to berate him for his cowardice; instead, Alastair told him of rumors that he was not Henry's offspring and was instead Charlotte's son with Gideon Lightwood.
After setting up an explosion with Christopher that would surely get him expelled, Matthew left with Will and James to the London Institute, something the Herondales agreed to after Matthew proclaimed his desire to become James' parabatai. The pair eventually became parabatai and grew closer.
The Fairchilds up and moved to their home in London so that Matthew could stay close to his parabatai. Christopher was also expelled for their stunt at the Academy, and Thomas did not attend the following year, and so the four of them remained a tight group and trained together at the London Institute.
Alastair's lies about the supposed rumors that he was Gideon's bastard affected Matthew more than he'd liked. He grew paranoid and sometimes had moments when he feared that his parents were separating. For a time, he even resented Gideon, refusing to think of him as his Uncle Gideon. During a trip to the London Shadow Market, recommended to him by good friend Anna Lightwood, Matthew came across Brother Zachariah, known to the Herondales and Lightwoods as Uncle Jem, and took it upon himself to get closer to him. They then came upon a faerie selling potions and charms. Matthew was particularly intrigued by a potion that he was led to believe would compel the truth out of someone and purchased it behind Zachariah's back.
Matthew put the potion into the cranberries for the scones he baked for his mother, hoping it would make her tell the truth about his parentage or the status of her marriage to Henry. As soon as Charlotte took a bite, Matthew realized that the potion was, in fact, a harmful concoction, just as Brother Zachariah had warned him that the fey could not always be trusted. While Zachariah overlooked Charlotte's treatment, Henry took Matthew aside to tell him that they had been expecting a daughter. He then told her that he hoped to name her Matilda, after his own great-aunt, from whom Matthew inherited his blond hair and for whom Matthew was named after, making Matthew realize that he was indeed Henry's son and not Gideon's.
Zachariah later told him that Charlotte survived, but the child in her womb did not. He advised Matthew to tell someone of the burden of his sin, but Matthew refused and feigned ignorance, though he carried the guilt—of having inadvertently caused his mother's miscarriage and for even listening to Alastair instead of trusting his mother.
Matthew is usually a delight to be around; open-hearted, sociable, flamboyant, and funny. He is also rather indolent, particularly when it comes to Shadowhunter activities. He is a natural caretaker, with a tendency to want and volunteer to look after those around him.
He can also be quite sensitive, and though usually expressed as a joke, he sometimes internalizes thoughts about his purpose. Matthew in his youth, despite his popularity and sociable exterior, was often self-doubting and insecure and thought so much of what others thought of him and believed they didn't care about him as much as he did, thinking he wasn't special to those that meant most to him.
- Nothing but Shadows (first appearance)
- Cast Long Shadows
- Every Exquisite Thing
- Chain of Gold (will appear)
- The Midnight Heir (first mention)
- The Land I Lost (mentioned only)
- A History of Notable Shadowhunters & Denizens of the Downworld
- See more here
- Matthew favors rapiers as his weapon.
- He doesn't like having his name shortened, to nicknames like "Matt" or "Matty".
- Matthew was named after his father's Great Aunt Matilda, whom he called Aunt Matty.
- Matthew has an interest in fashion, Downworlder haunts, and the bohemian lifestyle which he shares with Anna Lightwood.
- Matthew really wants to befriend Magnus Bane (but Magnus has reservations about doing so). 
- Matthew's favorite treat is Charlotte russe.
- Matthew is set to have younger sisters in TLH.
- Matthew was originally named Colin, and Matthew may have also been planned to be another character's name.
- Matthew originally was described as having brown eyes. However, his eyes are a dark green color in later publications. It is unclear if this is a change Cassie has made in his appearance since TftSA, or if his eyes simply appear different colors at times.
- ↑ 1.0 1.1 1.2 A History of Notable Shadowhunters & Denizens of the Downworld
- ↑ "Mathew - is Welsh," Cassandra Clare on Twitter
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 Cast Long Shadows
- ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Nothing but Shadows
- ↑ The Midnight Heir
- ↑ "He would never let anyone call him Matt" — Cassandra Clare on Twitter
- ↑ "SCANDAL. He is a MATTHEW." Cassandra Clare on Twitter
- ↑ Every Exquisite Thing
- ↑ Cassandra Clare on Tumblr
- ↑ January 2020 Shadowhunter Army Newsletter
- ↑ "As of TLH, Charlotte and Henry ... also have very young daughters." Cassandra Clare on Tumblr
- ↑ An answered question by Cassandra Clare on Tumblr
- ↑ Mention of Colin's name alongside Matthew's — Cassandra Clare on Tumblr