Why was Ham cursed for seeing his father naked? In Genesis 9:22-25, Ham's son Canaan was cursed because Ham saw his father (Noah) naked. The punishment seems excessive indicating there is more to the passage than meets the eye.
What did Ham do to cause Noah to curse his son, Canaan?
In the Old Testament, "uncovering the nakedness of your father" was a euphemism that was used for having relations with his wife. 

The likely explanation for this passage, based on my own study and consulting numerous commentaries of Bible scholars, is that, while Noah was drunk and unaware of what was going on around him, Ham entered his father's tent and had relations with his mother. Canaan was likely the result of that union, which explains why he was the target of the curse.

This explanation is not definitive, but it is the one that makes the most sense based on my study of the passage and the cultural underpinnings of the Old Testament.