The Shadow Children series by Margaret Peterson Haddix (beginning with Among The Hidden) were so good. Short, intense, with really vibrant and empathetic characters. I remember them really opening my mind to some really complex moral/ethical/political questions for the age range I read them at, which was like 10-12 I think. They made me think about things like, what moral lines would I be willing to cross to save my own life, how would I know the difference between rules that keep order and are unjust and rules that cause trouble but are just, and balancing the reality that there are good people on the “bad side” and bad people on the “good side.”
https://www.amazon.com/dp/0689824750/ref=cm_sw_r_cp_api_glc_fabc_JNicGbQGY745P
This is a long shot, but I remember reading a scene like that in Among The Hidden.
Idk if it’s the same one, but in my favorite “dystopian future” young adult novel, this happens. It’s called Among the Hidden.
Just [googled](/s "Forbidden Third Child book") ... the book is [called](/s "Among the Hidden"). Not sure where I got the "Night children"...