Filippo is introduced in City of Flowers as the second son of Matteo Nucci, who grew up in the great Nucci palazzo in Giglia and often played with his siblings and the di Chimici children. Often in the company of his brothers Camillo and Davide, he participates in the various festivities before the di Chimici weddings, including fencing tournaments where he faces Luciano Crinamorte. During one of his evening outings with his brothers, Davide is mysteriously stabbed to death by an unknown assailant assumed to be a member of the di Chimici family. While Camillo swears revenge for Davide's death, Filippo does not, though he begins aiding his father in amassing weapons for a potential conflict between the Nucci and di Chimici families.
When Camillo stabs Carlo di Chimici in the Church of Annunciation, Filippo retaliates when Carlo's brother Fabrizio slits Camillo's throat and winds up dueling Fabrizio and the Grand Duke Niccolo. In the fallout of the fray, Filippo is grievously injured and brought to the orphanage in Giglia serving as a temporary hospital at the insistence of Beatrice di Chimici. Despite Duke Niccolo's attempts to overrule Brother Sulien's wish to nurse Filippo alongside Gaetano di Chimici and Fabrizio at Saint-Mary-among-the-Vines, he gives in when Beatrice adamantly refuses to allow him to give such an order. However, Sulien keeps three friars around Filippo's bed to protect him. Through the intervention of Pope Lenient VI, Graziella is allowed to visit her son and remains in Giglia with Filippo's sisters until he recovers while Matteo is forced into exile, where he re-establishes himself through his connections in Classe.
In City of Ships, the extent of Filippo's injuries are revealed: he is badly scarred, including a long scar running from his temple to his chin, and has one stiff leg, forcing him to walk with a cane. However, he remembers very little from the Massacre at the Church of Annunciation, thus he does not hold a grudge against the di Chimici as his family does. His mother often worries about Fillipo's health, though Filippo tries hard to conceal his pain and find a way to become helpful to his family. He finds that he feels more at home in Classe than he did in Giglia.
After seeking out Fausto Ventura in hopes of become a mosaic master, Fausto senses Filippo's lack of talent and suggests to Germano Mariano, the Duke of Classe, that the young man may find some purpose with him. Germano assigns Filippo to become his envoy to Bellezza for the upcoming battle against the Gate People, where Filippo is reunited with Beatrice and a relationship blossoms. Filippo winds up befriending Isabella, a young Stravagante, and Andrea, a pirate, as Classe prepares for the upcoming invasion, and proves to be a loyal and trustworthy ally to the Bellezzans and the Stravaganti. Notably, when he finds Isabella's brother Carlo after he accidentally stravagates to Classe, Filippo discreetly provides Carlo with suitable clothing to disguise himself and brings the bewildered young man to Flavia for help.
During the Battle of Classe, Duke Germano is killed in the land battle against the di Chimici armies, resulting in Filippo rallying the Classe troops to repel the di Chimici army. For his bravery, he is awarded the highest honour of the city, the silver Victory Medal. At the request of the Classe Senate, he stands for election as the next Duke of Classe and is elected unopposed as Germano's successor, after which he marries Beatrice. He is mentioned sporadically in City of Swords as the governor of Classe; though he is Beatrice's husband, Fabrizio refuses to request help from Classe in the Siege of Fortezza out of aminosity towards the Nucci family. Filippo is also mentioned as one of the guests at the wedding of Luciano Crinamorte and Arianna Rossi.
Filippo is a very caring person and tries to be as helpful as possible, despite his injury. He is courteous and polite, being mindful of the feelings of other people. Unlike the rest of his family he does not hold a grudge against the di Chimici family for the Massacre at the Church of Annunciation, or the death of his two brothers, primarily from being unable to recall what he experienced during the massacre and his love for Beatrice di Chimici, whom he eventually marries. He is shown to be very strong willed and determined, though he is aware of his limitations.