You can do it different ways:
Sherlock Holmes' friend.
Sherlock Holmes's friend.
As we often pronounce it as a double s, the second form is more natural in this instance and so would be the preferred form.
The name Sherlock Holmes is a proper noun, the name of a specific person (character).
221b Baker Street Home of Sherlock Holmes.
In the novels of Arthur Conan Doyle, Sherlock Holmes was the famous sleuth. It's an old-fashioned word for "detective"
There was no logic in replacing the flimsy table with one just as weak. Sherlock Holmes used his observation, knowledge, and logic to solve crimes.
The detective character created by Sir Arthur Conan Doyle is Sherlock Holmes.(The pun used by locksmiths and realtors is "Sure Lock Homes.")
Sherlock Holmes's is the more proper form though Sherlock Holmes' is also acceptable. Please check the link below.
Estimated cost to make Sherlock Holmes (2009): $90 Million Estimated cost to make Sherlock Holmes: Game of Shadows (2011): $125 Million
Sherlock Holmes' real name is Sherlock Holmes.
Sherlock Holmes 3
.... Sherlock Holmes
Sherlock Holmes.
Sherlock Holmes
"Young Sherlock Holmes" (1985). Stars Nicholas Rowe as Sherlock Holmes, Alan Cox as John Watson.
Robert Downey jr has been in two Sherlock Holmes movies: Sherlock Holmes (2009) and Sherlock Holmes: A Game of Shadows (2011)
This is because the author, wanted to make Sherlock Holmes sound realistic enough for people to not think that he was fictional.
Sherlock & Holmes
The Adventures of Sherlock Holmes