They are both free spirits and determined. Percy's mother knows more about their past and is prepared to sacrifice herself for Percy. She sees the dangers that Percy faces while Percy knows very little about his past and what is going on.
Hope im correct
the main setting of the story sets the tone by allowing you to see that it is made during a time not as advanced as now but a few years ago. it symbolizes the lightning bolt stolen from Zeus. they differ in all natural ways and are in common by blood and physical appearance. he is supposed to protect percy and he does so. they are comparing her eyes to coals. in the last two chapters you learn that percy is the only child of Poseidon and that his father can grow in size.
I've read all the books if need any more help please let me know