1st -  starting from 14:57 Jong's eyes are on Key every time Key says something. EVERY TIME.
And you all know - it's so cute that it's not only this time but Jong always looks at Key when Key's talking and usually turns to Kibum when talking himself.
According to researches when you like someone you unconsciously turn your body towards them. And Jong does that a lot.
2nd - 15:54 - Key leans his head on Jonghyun's shoulder when laughing (and once again that's something he does a lot) and then Jonghyun leans his head against Key  and you can spot some affection if you look carefully because Jong did it for Key...like...it's not for the action itself if you get what I'm trying to say. Just watch carefully and you'll see it.