beta
Ok it isn't just me is it? They're foreshadowing really hard that Shi Hyun and Yoona might not be their biological children. I'm guessing in the past they were homeless and shi hyun was bothered with taking care of a small Yoona by himself and lost her so now he's just overly protective of her and maybe a little guilty for thinking of her as an annoyance before.
Source?
Ch 11. He specifically calls her his blood sister
Ch 18. There's a flashback of him letting go of her, if they were celebrities why wouldn't they have guards or assistants nearby?
Ch 41. He's being really defensive against there supposed "mother" and using clear distinct language like "my sister" and she picks up on that and keeps emphasizing she's their mom.