Perhaps degree of investment. Consider the amount of time it takes for someone to grow up, and the effort involved in teaching them (how to talk, read, etc.). (And before that, pregnancy.)
There is at least one book that plays with this—the protagonist finds out they were stolen from ‘their family’ as a baby (or really small child), and the people who stole them raised them, and up to that point they had no idea. I don’t remember the title.
Perhaps degree of investment. Consider the amount of time it takes for someone to grow up, and the effort involved in teaching them (how to talk, read, etc.). (And before that, pregnancy.)
There is at least one book that plays with this—the protagonist finds out they were stolen from ‘their family’ as a baby (or really small child), and the people who stole them raised them, and up to that point they had no idea. I don’t remember the title.