Shem et-Cham ve'et-Yefet - Shem, Cham and Yafet
Yafet appears to have been the eldest of the three brothers seeing that in 10:21 the Torah states, "brother of Yefet, the elder."
Cham appears to have been the youngest, as Torah writes in 9:24, "and he realized what had been done to him by his youngest son."
The reason Torah mentions Shem first was because he was the most outstanding of Noach's children. This is why Yafet had to be mentioned only after Shem.