Minor spoiler - not really - Recently in WMW and 'Hammer guy hides his strength' there has been a theme where the half sister or cousin wholeheartedly helps the heir of a family. Is this dynamic a reference to any other novel or event? I was just curious...
Not that I can tell? It seems like a fairly simple variation on the "friendly female relative who is juuuuust barely not-related enough to safely add to harem without grossing out too many readers". Edit: Maybe like little aunt of ATG?
Not familiar with these myself, but depends on whether it is an example of The Family That Slays Together or Coattail Riding Relative or maybe just the classic Father I want to Marry Brother. Everything is a trope if you study it enough; but I imagine it is not directly supposed to be one in this case.
Yeah, that was a stretch. Maybe I was just thinking of the first chapter. It seems a little more common in JP works.