There’s a WEBTOON that matches that description. It’s called I’m a Child of this house or something like that. It’s a girl sold to a duo tho not the king. She has blond hair and pink eyes whereas her dad has red eyes.
One correction it's a nobel not a king
http://www.mangago.me/read-manga/i_am_a_child_of_this_house/nto/to_chapter-1/
Duke*
It might be this?
http://www.mangago.me/read-manga/i_am_a_child_of_this_house/
Omg you all are so kind, thank you so much for all the help you all gave me! You all have made my day a lot brighter!
Ok so I started reading this manga and I can't remember what it's name was. It's about a girl who has been sold to a king by her mother because it's supposably his kid. The king pays for her. So she doesn't really look like him but I think she actually is his. One key detail is she is scared or water because her mom would lock her inside a box for hours and one day it started filling up and she almost dround. Thank you for any help you all give me in finding this!!