Wiliam Theiss Raymond was a Human. As the son of Scott Sendfonte Raymond and Hannah Shearer Raymond, he was the great-great-great-great-great-great-great-great grandchild of Clare and Donald Raymond. His brother was Robert. (TNG-R: "The Neutral Zone", okudagram)
The name of this character was never mentioned in dialog; the name came from the remastered Clare Raymond family tree. His name was an in-joke referring to costume designer William Ware Theiss.