Mercutio was an ambitious individual with a sly and snarky demeanor who aspired to become Montague's heir. He had contempt for common people and was tasked by Montague to spy on Romeo. Mercutio also appeared to have some interest in Hermione, but it remained unclear whether his feelings were genuine or if he planned to use her as a pawn in his potential plans. Mercutios desire for power seemed to stem from his resentment towards his father, Titus, who did not meet his expectations as a Montague advisor.
Montague was aware of Mercutio's disdain for his father and encouraged him, albeit subtly, to kill Titus. However, Mercutio did not carry out the deed. A few days after Romeo's banishment, Mercutio agreed to be adopted as Montagues new heir but was unprepared for the bloody initiation that culminated in Titus' death at the hands of Montague. Paralyzed by fear, Mercutio could not voice out for help or assist his father and later pledged loyalty to the bloodied Montague.
Despite trying to fit the mold of Montagues heir, the traumatic event of his fathers death left Mercutio deeply affected and riddled with guilt over his inaction. In an attempt to gain praise, Mercutio stabbed Montague and "saved" Juliet, only to be dismissed by Tybalt and left laughing maniacally.