Is it normal falling in love with a cousin?

I used to live in a small town. I needed some money to pay my court so i came to chicago to stayed with my aunt, uncle and cousins. First night i asleep on the floor in my cousisns room by the way they all girls. So she gave me a kiss =on the cheek and i did too. Next week at night we were giving kisses to each other in the forehead, cheek, nose. next week we were touching lips and that night we kissed in the mouth. we started to kissed eachother and having sex with clothes on, beacause she was younger than me for 7yrs. now we dont do that because she doesnt want her mom to be dissapointed on her. Is that a sin? should i tell her that i have feelings for her?