Complex

OK, so I have had a theory bouncing around my head since finishing, and I wonder what others think. Sorry if this is already posted somewhere. My theory is that honor was on another planet in roshar's system and was attacked my odium and fled to cultivation's planet with the humans. Cultivation maybe came to roshar and found an existing species and escalated them to dawnsingers (which would fit Sanderson's answers). In the letter from endowment to hoid, it sounds like the shards agreed not be on same planet So my theory is that honor isn't from roshar, and the spren are solar system wide which is why cultivation and him both have spren, and why the spren are many times from one or the other.