I don’t look like my parents yet the refuse to admit I was adopted.

I know it sounds weird, but I just know I’m adopted and my patents refuse to admit it. My parents are very white looking. And I’ve seen pictures and they always have been. We go on a vacation and their skin burns and peels. Mine browns more. I have brown skin. I look very ethnically different. I don’t know my actual ethnicity, but I’d say I look Native American. I have caramel colored eyes. They have blue and green eyes. I have an older brother and he looks EXACTLY like my dad. People always give us weird looks. I’m sure they think my mom cheated or something lol. But I don’t know what to do about it. I’m 16. I don’t care if I’m adopted. My parents are my parents and I love them and appreciate the great life I have. But I honestly just want to know for sure. I’m not positive as to how I deal with this. Any advice or suggestions on how to find out if I’m really adopted or not? By the way, when people ask why I look so different, my mom says I look like her great grandmother. I’ve seen pictures of her and that is not true! I know they are lying and it’s a bit scary to me honestly.