And Noah began to be an husbandman, and he planted a vineyard: And he drank of the wine, and was drunken; and he was uncovered within his tent. And Ham, the father of Canaan, saw the nakedness of his father, and told his two brethren without. And Shem and Japheth took a garment, and laid it upon both their shoulders, and went backward, and covered the nakedness of their father; and their faces were backward, and they saw not their father's nakedness. And Noah awoke from his wine, and knew what his younger son had done unto him. And he said, Cursed be Canaan; a servant of servants shall he be unto his brethren.
After Noah and his family get off the ark and are the only humans left, we get an odd tale about Ham's evil and the curse that came upon Canann (an enemy of Israel the rest of the Old Testament). What in the world does that mean? There are a lot of different options or theories about what really happened. Perhaps Ham did really see his dad naked, though one wonders if that is worthy of such a curse. Another theory is perhaps this means he castrated his father, which would certainly be worth some angst. Another theory is that Ham had sexual relations with his father, which certainly fits with the word choice as seeing someone's nakedness can mean this elsewhere. Or it may indicate maternal incest, as the language used here is used elsewhere in the Old Testament to denote maternal incest. There are examples elsewhere in the Bible of a son sleeping with the father's wife or concubine to usurp power, so it certainly was not unheard of. That would certainly result in some anger, but also explain the inclusion of Canaan, the son. In this theory, Canaan is the result of the incestuous coupling.
Of course, those are just theories. There are other places in the Bible we're just not sure exactly what was meant, such as at the start of Genesis 6:
And it came to pass, when men began to multiply on the face of the earth, and daughters were born unto them, That the sons of God saw the daughters of men that they were fair; and they took them wives of all which they chose. And the LORD said, My spirit shall not always strive with man, for that he also is flesh: yet his days shall be an hundred and twenty years. There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men which were of old, men of renown.One idea is that the sons of God were angels, and another theory would be that the sons of God were the men from Seth's line and the women were from Cain's line of evil. In either case, the result is the same. We probably won't know until we die, but we need to remember that an inability to understand this in its entirety is not a barrier to faith.