Then again, wasn't it said somewhere that Bowki never learned of his father's regret, or the cause of Dart's sorrow? I seem to recall something along these lines... but I ain't sure.
That being said, I am sure, no matter how innocent Bowki was claimed to be, that he didn't notice something was up with Dart. When a relative who is that close to you is depressed, you notice. Might not draw any hard conclusions, nor even ask why, but one knows that something is wrong.