User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-24205801-20121112034323/@comment-4902593-20121112055945

@67.7.115.191 The Titan's Curse takes place during December while Percy's birthday is in August. That means Percy is already 14 by the time of The Titan's curse. So Percy and Nico have an age difference of more or less, 4 years.Percy is close to turning 17 so that means Nico is around 13 I guess, around Hazel's age. He is older than Hazel by a few months.