My personal theory is that the original Wesley Trueblood (this man's father) was told that his name was simply too much, it's essence too powerful, so he legally changed his name to Wesley Trueblood junior. Thus, when his son was born, he didn't want to explain the full situation, so he just called his son Wesley Trueblood III.
Either that or his First name is Wesley, his middle name is Trueblood, and his last name is III
There are 2 people in the U.S. named Wesley Trueblood.
Either that or his First name is Wesley, his middle name is Trueblood, and his last name is III