When you are referring to two people named Sam, the plural form
is Sams, the plural possessive form is Sams'; for example: The two
Sams' desks are next to each other.
If you are referring to someone with the name Sams. Sams Smith,
or Sams Benson. Sams could be a name, but it is more likely that
you want to write Sam's. Sam's pen is blue. John's pen is black.
Roberta's pen is orange.