Am in love with my cousin – What should I do?

Please, I need you readers candid advice on this issue.
I met this really hot guy in a bbm group and we hit it off immediately. He wanted a relationship but we couldn’t have one because of the distance. He lives in New York and I, Nigeria. We kept in touch though. He was in Nigeria recently and we met briefly. He was everything I wanted in a guy.
Imagine my horror when I walked into my dad’s family house and saw him sitting with my grandma and my dad. The look on his face was indescribable when my dad introduced me as his daughter. We had not met earlier because my dad stopped talking to his elder sister (his mum) way before they got married over some stupid mistake my aunt made.
Apparently, he came back to settle the dispute between the family members. Now, he says he’s in love with me. We were always together through out our stay in my country home (our parents think it’s the same bond his mum and my dad shared when they were younger that extended to us).
How do I tell my family that I have been intimate with my cousin and that I’m in love with him? God knows I have done my best to forget about him but it’s just not working. I think about him all the time and he’s having the same problem! How do I let go of the only guy I have ever loved? I’m so confused!