No - the passport isn't enough. You need to prove that your father and your uncle are related. Many people share the same surname. Proving two people have the same surname doesn't prove they are related. You need to ask your uncle for a copy of his birth certificate.
1-my uncle's passport shows his ( surname \ FATHER NAME \place of birth )
2-my father's birth certificate shows his ( surname \ FATHER NAME \place of birth )
1-my uncle's passport shows his ( surname \ FATHER NAME \place of birth )
2-my father's birth certificate shows his ( surname \ FATHER NAME \place of birth )
If you do not find a common document showing your grandfather's name, then try to send as much documents as possible and write a cover note. Additional documents as such Marriage Certificate of your uncle n father and educational documents (that shows your grandfather name) and write a cover note explaining the relationship to be on safe side.