Quote Originally Posted by Vyrerus View Post
Each Lifestream is attached to the Aetherial Sea. This much is apparent due to Minfilia getting sucked into the Flow teleportation magic that spirits her through the Lifestream to the Aetherial Sea. And it is where Hydaelyn resides and keeps watch on all shards, so yes, it is.
The aetherial sea is the Lifestream, and the Lifestreams of each Shard are not connected for very obvious reasons. We have no reason to think Hydaelyn residing in the aetherial sea on the Source means that said sea is linked to the Shards.

Tenzen's soul was apparently bound up in Koryu's seal, so he can't have been an incarnation either.
In regards to both Tenzen and Ramza, we have some reasons to believe that apparitions of certain souls may be due to things like residual aether, or the manifestation of ambient aether through will similar to summonings. I think this was stated to be the case in a few instances of when we see certain spirits. Haurchefant and Ysayle on the Final Steps of Faith come to mind here, but I may be misremembering.