Do I Like Her?

I am 16 and never have had a girlfriend, but I don't think I am unattractive in any way. Except that I can be awkward and have some anxiety. But anyway, I have known this girl since elementary school, and one of her brothers (she's a triplet) is my best friend. My best friend and I go to the same high school, she goes to a different high school, and the other brother goes to another high school. I usually see her when I go to his house, which is pretty often because we live within a five minute walking distance of each other. When my mom takes the triplets and me for a night out, my mom always lets her sit in the front seat and make tie-breaking decisions on what we do. After we bring them home, my mom always comments on how pretty and perfect she is. Although she is pretty, she can be very shy and has some of the worst nerves and anxiety. Her mom playfully makes fun of us because we agree on everything and share the same thought processes, like procrastinating and being anxious over nothing. Over time, I am starting to think that I really like her, because she will make me nervous when I see her and I find myself always wanting just to hold her and take care of her and make her problems go away. However, I don't think she does or would like me back, because I know she has liked other guys and come close to dating them. Also, I'm worried about what this will do to my best friend and my friendship. So, do I like her? Should I talk to my best friend first? Other things? Thanks!