What is the correct writing of proper nouns in Henry neighbor who?

You are asking about the proper nouns in the phrase "Henry's neighbor who".

Here is the breakdown:

* Henry: This is a proper noun, a name of a specific person.

* neighbor: This is a common noun, describing a general category of people. It becomes a proper noun only if there's a specific neighbor with a name.

* who: This is a pronoun and not a proper noun.

Therefore, the only proper noun in the phrase is Henry.