YOU SAID:

it either is him or is someone pretending to be him

INTO JAPANESE

それは彼か彼のふりをしている人のどちらかです

BACK INTO ENGLISH

It's either him or someone pretending to be him

INTO JAPANESE

それは彼か彼のふりをしている誰かのどちらかです

BACK INTO ENGLISH

It's either him or someone pretending to be him