Added the parent-child relationship to post #1335774, though I'm not really sure whether to do that with posts under the tag derivative_work or not.
So are there some standards regarding that?
I read the wiki page for post relationships, but that didn't seem to say much about these kind of situations...

I'm not sure, either. The pictures are different, but the connection is quite obvious.

The artist's commentary said "I used ke-ta-sensei's art (post #1335774) as a reference."

This is derivative work at it's finest.