I think I get it, haha. I understand the basics at least through lots of exposure to Korean dramas :| and Japanese and Chinese systems are also a little similar.

Just two more questions! Is there a cut-off of sorts for what 'younger' is? For example, I've noticed that Yunho tends to just call Jaejoong by his name without any honorific attached, so does that mean their two-week age gap is short enough that the -hyung part is optional? Because Yoochun, despite only being a few months younger, uses hyung pretty frequently.

And second, what's the terminology for when a couple gets married then? Would a wife still call her husband oppa?