User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-108.75.104.200-20130120014228/@comment-74.134.149.69-20130120032027

Percy made them promise to claim their children by their thirteenth birthday, but that's not really the subject of the matter.

You're on the right track, but I think it's more about the gods simply cutting themselves off from everyone. While it's true that there's a lot about curses in this one, it's mainly about Hera specifically. Echo and Narcissus, Leo, Frank, Jason, Percy, Annabeth, Hercules... they were all cursed by Hera in some way or another (though it may not always be obvious).

Hazel's curse (at least the 'riches under the earth' one) was brought about by her mother's greed. Annabeth was cursed by Athena/Minerva to endure the Mark. Due to the mother/family factor, this is also seems like a small connection to Hera.

Because it's Hera, it just takes a small look into her domain of power to know where the story's going: Family.

In the end, pjo and hoo have always had a strong theme about family. I believe that, even though there are a lot of curses involved, the curses are used in a way to tell more about family matters than simply gods cursing mortals. Indeed, Calypso's curse was also brought about by her choosing sides with her family.

Hope this helped! :) And sorry for the long response. I have a tendency to do that sometimes...