Responses
I heard that Jiwoo's has been confirmed to be 17 in a live Q&A. But wiki says he's 18. (perhaps that's his Korean age, as it's +1). And Jiyoung is 21 (Korean age? at wiki).
Her brother is 1 years older than Jiwoo. And Kayden doesn't know his own age & birthday (confirmed by author)
I personally don't want to ship them. Not even in the future (￣∇￣"). I rather have her as his big sis than a love interest. So, I hope the ship won't sail & just stay as an awkward crush LOL
I know their age gap isnt too big (I dont remember they mentioned the exact gap though) but jiwoo is practically still a minor, so its kinda weird. make it years later if they want to make the ship happen