From M'Benga's memory alpha page:
[M'Benga] was actually created by
Darlene Hartman, in her purchased (but never produced) TOS script entitled "
Shol". The notes for that script give Dr. M'Benga's first name as "Joseph", and stated that he was originally a native of Uganda. His brother, Commander Simon M'Benga, was the
first officer of USS
Hope, a Federation hospital ship, in the planned-but-never-developed
Star Trek spinoff
Hopeship.
Curious if there's any chance of these ideas making it into new Trek now, although probably not as they'd have to pay royalties to Ms. Hartman (who Memory Alpha indicates is still alive)