Do you think I'm adopted?

I've heard that kids can't have darker eyes than their parent, but my mom has blue eyes, dad brown, I have blue, my twin (fraternal) has brown, younger brother brown, and youngest brother blue. I don't act like anyone in my family, or look like them, they all have dark hair, and I have red. I am always pale whereas in the summer they all get veryyyy dark. I have a cousin with red hair, if that matters. And I've also seen my birth certificate, but I'm still a bit wary. What's your opinion?