Nidhogg is kind of an outlier tbh, and the questline I'm thinking of is in fact, his brood returning for their dead.
The dragon lifecycle is all sorts of fucky but I do think it's fair to say dragonet is probably equivalent to like somewhere between toddler and elementary school in RL human terms. We're not sure why some dragons become wyrms or dragons or wyverns or amphipteres etc. Of the top of my head the following should be sentient draconic lifeforms: celestial dragons, adamantoise dragons, amphipteres, brobinyaks, coeurldragons, dragon dragons, dragonets, falaks, vishap, tioman, shield dragons, ancient wyverns, elder wyverns, vouvires, and wyverns. Weredragons (aevis, diresaur, syricta) are all men-into-dragons so ofc they're sentient.
For simplicity's sake I'm going to start saying Spoken, since that's XIV's term for a sentient being (beastmen, mankind, etc). Anyways the "feral" dragons should be shit like: archaeornis, archaeosaurs (incl vinegaroons), dragonflies (xi puk), drakes, elbsts, hydras, peistes and maybe raptors/endymions. Those aren't "true dragons" (as far we've been led to believe-- Hydras are in a fucky place atm) but beasts sort of brainwashed by dragons. They aren't part of the dragon lifecycle.
Anyways here are like a thousand reasons Bahamut was strong: sustained prayers of imprisoned children that may or may not have been clones, the original summoning utilized a shitton of aether via Tiamat's eyes, using the Crystals of Light explanation we know Hydaelyn was stronger in Eras past and we know Primals 'steal' Hydaelyn's aether to form--therefore Primals summoned in earlier eras are default stronger, the Ascians taught a stronger ritual to Tiamat b/c they knew she could pull it off, etc.
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