User blog comment:Percy Jackson12/The Seven/@comment-4525239-20111015093403/@comment-3146930-20111015134949

Actually they were all sons of Posiedon. Arion was originally a child of Poseidon and Demeter and Franks ancestor was Greek. Percy and Tyson are also sons of Poseidon and so was Phineas. I dont think there was a single son of Neptune in that book. Lost Hero had 2