John Wesley on Genesis 9:25

A servant of servants - That is, the meanest and most despicable servant shall he be, even to his brethren. Those who by birth were his equals, should by conquest be his lords. This certainly points at the victories obtained by Israel over the Canaanites, by which they were all either put to the sword, or put under tribute. Jos 9:23 Jud 1:28,30,33,35, which happened not 'till about eight hundred years after this. God often visits the iniquity of the fathers upon the children, especially when the children inherit the fathers wicked dispositions, and imitate the father's wicked practices.