The Wikipedia page for Liu says:
劉 / 刘 (/ljoʊ/ or /ljuː/;1 romanised as Liu, Lau, Leo, Ryu, Yoo, Lew, Lieu, Liou, Liw) is a Chinese surname. Liu as transcribed in English can represent several different surnames written in different Chinese characters.
As you can see the surname has been Romanized in many different ways, including: Leo. So, 刘 would be the simplified character writing for Leo while 劉 would be the traditional character writing for Leo.