Bellerophon

Bellerophon is a famous son of Poseidon.

Early Life
Bellerophon was born in Corinth. He accidentally killed a man named Belleros and earned this name, meaning 'the killer of Belleros'. He also accidentally killed his own brother and was sent to a neighbouring kingdom to atone for it. The queen of that kingdom fell in love with him and when he refused her proposal, sent him to her father's kingdom where she asked him to kill him immediately.

Percy Jackson's Greek Heroes
Bellerophon is asked by the father of the jealous queen to  slaughter  The Chimera, a monster terrorizing the kingdom at that time. Bellerophon, knowing The Chimera will burn everyone that comes near it with it's fiery breath asks the wisest man in his kingdom for aid. He says that Bellerophon can capture the immortal lord of horses, Pegasus if he goes to a certain point. So Bellerophon grabs some lead and heads out to the place. After waiting all night, Bellerophon awakes to see the goddess Athena standing at his aid. With Athena's help, Bellerophon captures The Pegasus and rides out to meet The Chimera. The Chimera, as soon as it sees Bellerophon breathes out fire but the Pegasus hovers out of the way. Bellerophon drops the lead he collected into Chimera's mouth where the hot breath of the monster melts the lead into poison sludge which Chimera swallowed. The Chimera slowly suffocated until it died. The king then gives him two more challenges which he willingly accomplishes. Delighted, the old king gifts  Bellerophon his daughter in marriage. The couple had a good life together but one day, Bellerophon rode on Pegasus and shouted that he was equal to the gods. Zeus overheard this on Mount Olympus and was enraged. Therefore, the king of gods summoned a lightning bolt which stung Pegasus, causing the horse to rear, throwing Bellerophon off and causing the demigod to fall to his death.

Personality
Bellerophon, like all demigods, is ADHD. He is also described to be exceptionally clumsy, as he killed his own brother and an innocent man unintentionally. He also has good morals as he rebuffed the queen's flirting, knowing his limits as a guest and sticking to them.