User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-7153535-20130629173532/@comment-3146930-20130707113409

Also, when Percy and Nico meet again in The Son of Neptune, Hazel comments that despite the camp thinking he was an oddball traveler, she could tell that he may be even more dangerous then Jason. Also take into account that Nico is 2 years younger then Jason, and 3 years younger then Percy (yes, I know he is like 70 years old, but physically he is only about 14).