Any novel or manga that focuses on being an illegitimate child or people living with second families Historical is preferred but I'll also consider one from modern or different times. I just love family dynamics. Thanks in advance for those who will reply.
inverted dragons scale mc is legitimative child that is sick and they switcheroo him for servant girls modern time with diffrent world
More like...stories with children and family stuff than what you wanted: If It’s for My Daughter, I’d Even Defeat a Demon Lord From Maid to Mother Isekai Yururi Kikou ~Raising Children While Being an Adventurer~
Monarch of Evernight is something you might like. Mc is an illigitemate child of an aristocrat family and also has an adoptive father who is not a part of it but the story hasnt fully explored it in the translated chapters yet. You might also like City of Sin aswell.