How normal is it to date your third cousin?

So I met this guy through an art program, and we started talking and hanging out a lot. I realized he is pretty close to the right person for me, exactly what I look for in a guy to date. After dating for only a couple days, my mom asked me what his last name was, and I told her. She proceeded to make the connection and tell me that we were related, which she found hysterical. I was mortified. A couple seconds later, I called him to tell him. He then started to freak out too, and he called his grandmother to confirm it, and she did. We figured out that we have the same great great grandfather and are 3rd cousins. He called his brother and his aunt to see what they thought about us dating, and both said the thought it was a funny coincidence but we were distant enough to date. He told me that he was ok with it but that he could tell I was still weirded out by it. I am weirded out some, but i like him enough to try and get over it. I am not looking for a serious relationship with him, but would like to continue seeing him. Is it normal to date my third cousin????