Does Takahashi ever state which brother (Inuyasha or Sesshomaru) is the true heir to the “Western Lands”?
Well, if the Hyakki Bats in Vol. 22 are any indication of how most demons work, they seem to just find a place they like, claim it, and then kill any nearby humans. I imagine this is probably how their father operated as well. Of course, he more than likely tried to avoid killing humans since he was married to one and had Tetsusaiga created to protect human life. Sesshomaru, however, would probably be the one entitled to their father’s domain since he was oldest and also a full-blooded demon.