I know that Luis Rodriguez and Doug Vaillant were suppose to be half-brothers, and they both fought for World Titles in 1963, so I will go with that. Rodriguez was one of my favorite boxers.
You are correct, sir. The half brothers is the tricky bit. :good It's interesting to note that they both challenged for the world title for very first time just a few weeks apart.
Here's the questions that are still unanswered: What former heavyweight title challenger had a daughter drafted in the 1st round of the WNBA draft? Here's another one: What was the 1st world title fight tracked by compubox?