Hydaelyn and Midgardsomr

[SilverArrow20XX]

Midgardsormr arrived to Hydaelyn with 7 eggs.
By the 3rd Astral Era, the First Brood had already been around for a long time. Each had their own broods already, and were waging war with Allag.
Midgardsormr himself says he arrived at the beginning of time if I recall.
It's unclear when this is though.
I would say 1st Astral Era at the latest, but likely during the Age of the Gods. After the Sundering, but before the 1st Umbral Calamity. During Good King Mog's time.
I would even go as far as to say that the "Gods" the Moogles served in the Churning Mists before their exodus following the 1st Umbral Calamity were likely dragons.
I like to think all 7 of the First Brood resided there in the beginning when they were hatchlings. With Bahamut and Tiamat later leaving and making their home in Meracydia.