Who was the "small son" whose deed Noach realized when he became sober?
Rashi: Cham, who was the smallest (in his behavior), the most contemptible of his children.
Seforno: This refers to Kena'an, the youngest of his grandchildren. 1
Moshav Zekenim: It is Kena'an, the youngest son of the one mentioned above (Cham).
QUESTIONS ON RASHI
Rashi writes: "... his rejected, insignificant son." Why did Rashi not interpret the verse literally, that Cham was the youngest of Noach's children?
Mizrachi: Cham was in fact older than Yefes. 1
Gur Aryeh: In the next Perek (10:11), it is clear that Yefes was the eldest [and Cham was in fact the youngest]! Rather, Rashi does not interpret literally here, because that fact is irrelevant in the context of this verse.