Why does the Torah see fit to mention here, the fact that Cham was the father of Kena'an?
Rashi: Because the Parshah is about to record the episode of Noach's drunkenness, in which his son Cham, sinned, as a result of which his son Kena'an would be cursed. Had the Torah not informed us first, we would not have known who Kena'an was. 1
Seforno: To explain Cham's behavior (in the forthcoming Parshah); the Torah is telling us that Cham's characteristics resembled those of the infamous Kena'anim - to the extent that he was in fact, the father of Kena'an.
Ramban #1 (citing the Ibn Ezra) 2 : Although it was Cham who spread the news of his father's nakedness, it was his son Kena'an who acted upon that information, 3 (although the Torah does not tell us so explicitly).
Ramban #2 4 : In fact, Cham was the youngest of Noach's sons 5 , and Kena'an was the oldest of Cham's sons. 6 When Cham did what he did, Noach punished him by cursing the one son that he had at the time (Kena'an with all his descendents). Noach considered that sufficient punishment, and declined to curse all of Cham's future offspring. 7
This answer is problematic however, seeing as the Torah repeats the fact that Cham was Kena'an's father (9:22) before he was cursed. So why mention it here?
When the Torah writes that "Noach knew what his youngest son had done" (9:24), it refers to the youngest son of Cham, who was mentioned two Pesukim earlier.
The Ramban himself cites 9:22, leaving us with the question that we posed on Rashi (above, note 1).
According to Ramban; refer to 6:10:2:1; also refer to 10:21:3.3.
The Torah only mentions him last (Bereishis 10:6) because he was cursed.
Had he cursed Cham, that would have included any children that he may (or may not) have fathered from now on, but not Kena'an, who was already born.
