who’s son is siwoon again?

His mom and dad ╮(￣▽￣)╭(▰˘◡˘▰)

I mean it's not lie ╮(￣▽￣)╭

Not one of the main cast. He is an old childhood friend of Byul's who grew distant for some reason.

As a little Easter egg, him and siwoo were close as children in the love is fantasy story, and even got fake married