User blog comment:Darkcloud1111/It's All Connected/@comment-4578774-20111107211646

I believe it could be Annabeth because they have a single demi-god from one god, Percy is from Poseidon, and he is the only child from Poseidon. Hazel is the only child from Hades/Pluto. Piper is the only child from Aphrodite. Leo is the only child from Hephaestus. Jason is the only child from Zeus/Jupiter. I believe it's Annabeth because the book is called The Mark of ATHENA and Annabeth is the only child of Athena that is mentioned and focused on in both series. Agree?