Simon is a knight of House Tarth and the eldest son of the heir, Endrew of Tarth. He has a sheepdog named Puck and a younger sister he trains with sword and shield named Shyra. His grandfather is Lord Selwyn the Evenstar.
He has dark hair kept cut cleanly above his shoulders, sapphire blue eyes, strong features, and a defined chin, but his boyish charm is still visible.
Upon being granted the position of squire, Simon's father, Endrew, first arranged for his son to serve his youngest brother, Ser Quentyn of Tarth.
Simon, still serving as a squire for Galladon, left the Isle of Tarth for the first time to see real battle. Ser Galladon Tarth was in command of men sent to join Lord Orys Connington and Lord Corliss Caron, Simon's maternal cousin, in what later became known as the Nightsong Conflict. Simon served by his side as squire.
Following the Nightsong Conflict, Simon was knighted by Galladon for his assistance in retaking House Caron's castle.
In an attempt to foster good relations between fellow Connington loyalist houses, Simon's father arranged for his son to take on a Morrigen named Gawen as a squire. Gawen was close to Simon's age and the two grew close quickly.
Simon was among the many Stormlanders to attend the Tourney of Blackhaven. There, he witnessed his cousin, Durran Dondarrion's death. Following Durran's funeral, he and his other kin ventured back to Evenfall Hall at his father, acting lord-regent Endrew's command.
Gawen was ordered to return home by Endrew, following the murder of his kin by Lord Seaworth and despite Simon's protests to have him remain on Tarth.
During a council metting between the many Tarths, Simon's father and uncle disagreed on who House Tarth should support in the growing conflict in the kingdom. Simon agreed with Galladon that House Dondarrion deserved their support, but Endrew backed House Connington instead with the support of most of their kin, including his visiting aunt, Lady Jeyne Buckler. Simon sat silent as his father put Galladon under house arrest, but soon wrote to Blackhaven to tell them of his fate. At Alyn Connington's funeral, Simon was the only stormlander to speak up when Orys Connington declared Uthor Dondarrion guilty of treason. Following the funeral, Simon snuck into the ravenry and sent another warning to Blackhaven. His aunt Jeyne assisted him in distracting the maester, revealing she too cared for the safety of their Dondarrion kin. Jeyne then went on to convince Endrew to allow her to take Simon on as her sworn sword, instead of him serving as a foot soldier in Connington's assault on Oniontown. Simon was under the assumption he was returning to Bronzegate with Jeyne, however, along the kingsroad, their party split. Jeyne introduced Simon to her other knight, Ser Alvyn of the Kingswood, and instructed him to part ways with her. He was angered by the deception, however agreed once Jeyne told him of her plan to send the knights back to Evenfall Hall and free Galladon from imprisonment, allowing them to join Uthor's growing army. Once reaching the Sapphire Isle, Simon succeeded in convincing the Castellan of Evenfall Hall he was there under orders of his father and Orys to take custody of Galladon. He freed his uncle, but Galladon urged him to take the plan further and seize Evenfall Hall for himself, in order to declare all of the Sapphire Isle for the rebels. Simon agreed, despite his severe hesitations in not following his aunt's plan. Galladon and Simon began by arresting the Castellan. Galladon then gave an impassioned speech that riled the castle to the their cause. The pair spent the next few weeks raising the levies and calling their banners, however, they were forced to retreat to within the walls of Evenfall Hall when word of the Tarth fleet's arrival on the isle reached the castle. Endrew arrived shortly after, accompanied by Arthur Connington and an army, who were forced to land on their way to Rain House following a devastating storm. Galladon and Simon closed the gates and turned them away, finally revealing to the rest of The Stormlands they had declared themselves for the rebels. Endrew was enraged, and began to besiege the castle.