Do the Scions know? (Spoilers)

[Veloran]

Taynor didn't awaken the Echo during the 5.3 starshowers, Unulkalhai has it. They are both 1/14 soul shards. If Taynor was a shard of the same soul, he'd have awakened to the ability. Therefore, different souls.

There's really no consistency or hard rules regarding the Echo and awakening it, or anything saying that the same soul will always gain the Echo.

Also even if they're both "1/14" there's actually reason to believe that all shards are not created equal, as with the description we're given of Hydaelyn's power to sunder things it's actually dividing things in half. This would mean the First, as the first shard sundered from the Source, actually has half the aetherial density of the unsundered world, while the Thirteenth, being the last sundered shard, would have like 0.001% the density of the original. The point here is that assuming them to be exactly equivalent is debatable.

[DPZ2]

Also even if they're both "1/14" there's actually reason to believe that all shards are not created equal, as with the description we're given of Hydaelyn's power to sunder things it's actually dividing things in half. This would mean the First, as the first shard sundered from the Source, actually has half the aetherial density of the unsundered world, while the Thirteenth, being the last sundered shard, would have like 0.001% the density of the original. The point here is that assuming them to be exactly equivalent is debatable.

Explaining the mathematics behind the sundering of shards has been a time-honored pursuit of methodologies behind the "Hydaelyn Complex" conspiracy since the Moogles left their homeland during what we now know as "the Great Blowing". Unfortunately, empirical evidence of that Event is only provided by the number of papers written about the conjectured aetherial density differences between "Shards", whatever those may be. In this work, I will attempt to prove that one of fourteen is, indeed, 1/14.

- Daneel Than, The Mathematics of Wind, Eorzean Press, 1577.