User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-7153535-20130628164327/@comment-6064271-20130629001553

Ok but in lightning thief Chiron says that they are the big 3 because their children end up being the most powerful demigods as World War 2 was a war between the children of Poseidon and Zeus vs Hades. Chiron made Percy believe that this was the reason they decided not to have kids. Now that i think of it thats probably the true reason why they didnt have alot of children in their roman forms. Not because of the prophecy but because of the wars their children were causing.