The MLA Handbook advises, in section 6.2, “In parenthetical citations, use only the part of an author’s name—usually the surname only—necessary to find the entry in the list of works cited” (229). If your works-cited list contains only one entry under a particular surname, that surname will suffice on its own in your parenthetical citation. For example, if you’re citing an interview with the actor Jason Robards, Jr., and are citing no other Robards, do not include “Jr.” in the parenthetical citation, because “Jr.” is not part of the surname and is not needed to identify the correct source in your works-cited list.
If you cite two authors with the same surname and different first names, follow the guidance in the MLA Handbook to include the author’s first initial in your parenthetical citation (6.7). When your cited authors have identical first initials or identical given names as well as identical surnames, you’ll need to include more information. (Before we look at some examples below, remember that sometimes naming cited authors in your prose can simplify parenthetical citation. Include the cited author’s name in parentheses only if you haven’t specified it in your prose.)
For example, if your works-cited list includes interviews with Jason Robards, Sr.; Jason Robards, Jr.; and Jason Robards III, you’ll need to identify those authors as (Robards, Sr.), (Robards, Jr.), and (Robards III) respectively in your parenthetical citations. If you also cite Sam Robards, you’ll need to add first initials to those citations—for example, (J. Robards III) and (S. Robards). Finally, if you cite Jake Robards along with one or more of the Jasons, first initials won’t give readers enough information, so you’ll need to include full given names in your parenthetical citations or in your prose: (Jake Robards), (Jason Robards, Jr.), (Sam Robards), and so on.
MLA Handbook. 9th ed., Modern Language Association of America, 2021.