a realization

Each one of us are unique. Not because you are different from your other siblings doesn't mean that you are already adopted. I have 6 other siblings and all of us act differently and even don't look the same or has the same characteristics. So don't feel sad or think anything bad because all of us are unique.

I don't think you are adopted. A child learns from his/her environment. This includes but not limits to families, friends, school, and church. This cognitive learning from the environment contributes to one's personality, though it won't totally determine it. Adult decision-making and experiences can also mold once personality. The way you act is much more heavily influenced by your habits instead of your genes. Besides, it is well known in genetics that an offspring might not look like the parents. This is because of the possibility of inheriting the dormant genes of both parents. Gosh, I'm going too technical. Ok, let's just change view points. Don't worry about it. It hardly matters. Perhaps it mattered when you were younger whether you are adopted or not. As you grow older it becomes less trivial. What matters most is you and yourself. Besides, you are living your own life, not your parents or siblings. Enjoy life!