со своим братом

with one’s own brother

→ с
phrase Rare #36,505
with one’s own brother Uses the reflexive possessive своим to show that the brother belongs to the subject of the sentence.
RU: Он гуляет со своим братом.
EN: He is walking with his brother.

Том сидит рядом со своим братом.

Tom is sitting next to his brother.