For those who figured they were adopted on their own, what made you 'feel' you were not a biological child?

Question

Most of us grow up with assumptions that our parents are our biological parents. For those who were adopted, prior to being certain, what did you assume? Did you assume that your parents were your biological parents, or was there strong assumption that they were not?

Answer 1

Ever had a roommate?  Or a co-worker?  Or a mailman?

What made you assume they were not your mother or father?

Get it?

Answer 2

Why do so many adult female animals reject the offspring of another adult female. Its biological instinct.

Answer 3

I can't answer your question, but I can tell you that even biological children sometimes feel like there is no way I'm related to these people.