The crux of the original part of LoreHunter’s argument (from my understanding) is that because the Grand Navy arrested Nero, that must have happened in the past 20 years, as the Grand Navy was said to formed about 20 years ago. This means that Calvus, which took the reign at age 11, must not have been in rule for more than 20 years.
This means that the very maximum (assuming Octavious only ruled for 1-3 years) is that Calvus is 31, and his rules was 20 years, and that his oldest child (which vetex said the oldest was 2 iirc), would have been born when he was 29.
Because his oldest child was about 2, this means that the youngest he could be is 20, and he had his first child at 18. This would make his rule have lasted 9 years. This makes about a 10 year window where things could line up, assuming Nero being arrested is the same time Octavious took the throne.
This is why mentioning his children is important for the argument, and when he had them. There is no evidence of when he had children, except that his oldest was two years before we fought him, which is all we need to know.
Both General Argos and Gallio Bronze recall time spent under the reign of Octavious. If Calvus were to be catastrophically old because he is a mage, then these two would not be able to, since they wouldn’t have been around. But also it is impossible for Calvus to be really old for reasons mentioned above.
Gallio Bronze, a prisoner in the Eternal Mines, who we speak to as part of the quest, specifically says that it was more than thirty years ago. This would be impossible for reasons specified above.
Of course, this is all assuming Nero being arrested and Nero leaving the throne occur at the same time. I, personally, believe that Nero lost his throne before being arrested, but there are also reasons to believe that he wouldn’t have left the throne. Either tech or vetex will say something, or we’ll just have to wait for a definitive answer when we learn more about Nero in the future.