If the reference list includes two or more first authors with the same surname, include the first author's initials to separate them in all in-text citations, even if the year of publication differs. This helps avoid confusion and helps the reader locate the correct entry in the reference list. 

• This opinion is held by J. Smith and Thompson (2006) and is also supported by C. Smith (2005).

For more information: APA style: Citing Authors With the Same Surname