Is it normal that i cannot stop loving my best friend?

Ive been best friends with two people my whole life. Since we were kids we were hangin out and such, and pretty much saw each other grow up. You see, the three of us are together all day. We cant be separated. They are brother and sister. Shes the oldest of us. She's 20 im 19 and her brother is 18. My problem is that i cant sto loving her. I came to terms with myself that i love this girls so much that as long as i can have her in my life as just a friend it would be better not having her at all. Most of my happiness comes from seeing her happy. I smile when i see her smile and I melt inside when i hear her laugh. Ive had many gf's and became pretty close to a few of them, even one that lasted 3 yrs. But this girl is a completely different feeling. It;s not even so much a physical attraction although she is very beautiful and, well, i hate using this word to describe her, but she's super hot. I feel like i can literally say i love every aspect of her. I would do anything for this girl. Now a few details, we have talked about our feeling before. a long, long time ago. i think we were like 11 or 12 and we confessed to each other that we had feelings to each other but we both decided it was best to stay friends to save our relationship. and we did and went off and matured sexually with other people. But now that we both have been single for over 2 years now, and started spending even more time together my feelings came back even stronger. like this urge ive never felt before. I dont know what to do or say or how to even go about this. i feel in my heart that we will end up together one day, i think everyone does. But im scared its something im just telling myself to feel better. What if im wrong? what if im right? if im right, how long will i have to wait? if im wrong, why do i feel this way. she makes it hard for me to get over her. ill be laying on the couch watching tv and she will come and sit right next to me and either lean on me or put her feet on my lap or she would rest her arms on my lap and put her head on my chest. shes so comfortable around me she walks out of the shower in a towel or sometimes just undergarments now cmon! is that really fair?! In fact it seems like she always has to be touching me. but idk if girls do this normally with their guy friends. we have everything in common and she even calls me honey and i call her babe. the only thing pretty much missing here is physical romantic contact and some sort of agreement of some sort i guess? im just very confused. What should i do? tell her how i feel? wait and see what happens? should i believe what my heart tells me? are any of the things i said a good sign or should i stop feeling special? what should i do, world?