своих одноклассников

one's classmates

→ свой
phrase Rare #42,266
one's classmates своих is the genitive plural form of свой, meaning “one’s own”; the exact English possessive depends on the subject and context, such as “his,” “her,” “their,” or “my.”
RU: Я часто вижу своих одноклассников после школы.
EN: I often see my classmates after school.

Том отличается от своих одноклассников.

Tom is different from his classmates.

Том выше всех своих одноклассников.

Tom is taller than all his classmates.