So I went on Jay Joonhyung Kim instagram and I’ve noticed he had photos w/ Hyoyeon way before this news about them dating started
(this one dates back to Janaury 22)

(and this one dates back to Feb 17)

So I think they’ve been dating since the beginning of 2013. And that the vacation thing is what got them noticed/caught…My spidey senses are telling me that this is info is correct.