Honestly even if it's for the convenience of the plot, it's just ridiculous how their father was able to predict and lay out every freaking moves and paths for his sons to play into
I have yet read here a youkai or a god or any of those supernatural beings being able to see then plan into the future. So I refuse this. But it's a good story anyway. Still, imagine one cog falls off, and whoops, we ain't here no more.