How can you figure out if your parents are your actual parents with out getting a DNA test?

I want to know if there are ways to figure out if my parents are actually my parents with out getting a DNA test. I have looked at my birth cirtificate and my parents names are on it. And my mom says I am her child. But I am not convinced that I am their child. I am nothing like them in any shape or form. And if you look at my brothers and sister, you can tell that they are my parents children.