User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-24205801-20121118053718/@comment-3146930-20121124062052

Actually, Percy and Annabeth are cousins. So Zeus and Poseidon are brothers, meaning any children they have would be cousins. So Athena and Percy are cousins and Annabeth is Athena's daughter, so her and Percy are cousins-once-removed (I think that is the right term).

Also, Aphrodite and Hephaestus are married, but that would mean that all their children are Step-Siblings, not Half-Siblings. Aphrodite could be considered Kronos' sister, as they were both born from Ouranus. Based on that, she is the Aunt of Zeus, Poseidon, Hades, Hera, Hestia, and Demeter. That means she is the Great Aunt of Hephaestus. Based on this, all her children are Hephaestus' aunts or uncles and the Great Aunts/Uncles of all his kids, plus they are all step-siblings.

And lastly, Chris is a son of Hermes and Clarisse is a son of Ares, so they would also be cousins. Hazel is Frank's Aunt, not Great Aunt.