What are signs that you're adopted or switched at birth?

I don't look like my parents or brother at all. Whenever people see me and my brother together they say we look nothing alike. I just checked with both my bro and mom, and they both have attached earlobes while I have unattached earlobes. I've also felt like the black sheep, the one that didn't belong because our personalities don't match at all. My interests are completely different from those of the family, I'm an unconventional person overall while everyone else is very traditional. The truth is I kinda want to be adopted, or actually half related to my brother.. I hated my childhood :/ Maybe I have a different father? Or maybe I was switched at birth and my parents were unaware? People never guess that I'm related to my family!