“fathered Shem, Ham, and Japheth.” Although Genesis 5:32 seems to say that all of Noah’s sons were born when he was 500 years old only the oldest son, Japheth was born at that time. This can be clearly seen by studying all the scriptures on the subject (see commentary on Gen. 10:21). Japheth is said to be the oldest brother in Genesis 10:21. Also, Ham is said to be the youngest son in Genesis 9:24, where the word “younger” is better translated as “youngest.” Shem is listed first in this list because of his spiritual priority in being the line to the Messiah. Ham is apparently listed second because of the relationship between the descendants of Ham and the descendants of Shem in the Bible. For example, the Egyptians and Canaanites were descendants of Ham, and they consistently interacted with the descendants of Shem.
The flood came when Noah was 600 (Gen. 7:11-12). Since Genesis 11:10 states that Shem was 100 years old two years after the flood, Shem could not have been born when Noah was 500, because then Shem would have been 102, not 100, two years after the flood. It was Japheth that was born when Noah was 500, then, the year of the Flood Japheth was 100 and Shem was 98, then Shem was 100 two years after the Flood (see commentary on Gen. 10:21).