Where can I find a family tree to find people related to Chinese Emperors?

My friend, who came from China said he was related to Cao Pi of Wei, I wanted to know if that was true. Also, I wanted to find out how to see if certain people were related to eachother. (I wanted to see if Lu Xun, Lu Su, Lu Meng, Lu Fan, and Lu Bu were all related somehow)|||Ancestory.com