The Lightning Thief
How we cite our quotes:
"When Hades found out about the girl, he wasn't too happy about Zeus breaking his oath. Hades let the worst monsters out of Tartarus to torment Thalia. A satyr was assigned to be her keeper when she was twelve, but there was nothing he could do. He tried to escort her with a couple of other half-bloods she'd befriended. They almost made it. […] All three Kindly Ones were after them, along with a hoard of hellhounds. They were about to be overrun when Thalia told her satyr to take the other two half-bloods to safety while she held off the monsters. She was wounded and tired, and she didn't want to live like a hunted animal. The satyr didn't want to leave her, but he couldn't change her mind, and he had to protect the others. So Thalia made her final stand alone at the top of that hill. As she died, Zeus took pity on her. He turned her into that pine tree." (8.71-72)
Family is what causes much of the conflict in this story. Percy's very existence is offensive to Zeus and Hades. And Percy doesn't even know his dad very well at all! When Poseidon tells Percy he doesn't wish a demi-god's life on him (when they chat on Mount Olympus), we only have to look to Thalia's story to know what he means. The life of a demi-god is tough. You straddle two worlds, and you are forever hunted by monsters. How do Percy and Annabeth's mortal families compare with the immortal family we learn about?