restrictive/non-restrictive

[navi tasan]

1-My brother whose name is John is arriving tomorrow.
2-My brother, whose name is John, is arriving tomorrow.

3-My brother who works at the post office is arriving tomorrow.
4-My brother, who works at the post office, is arriving tomorrow.

In which case:
a-I have only one brother
b-I have more than one brother
c-One cannot tell

[5jj]

]1-My brother whose name is John is arriving tomorrow. You have more than one brother. This is a very unnatural-sounding sentence.
2-My brother, whose name is John, is arriving tomorrow. You probably have one brother,

3-My brother who works at the post office is arriving tomorrow. You have more than one brother.
4-My brother, who works at the post office, is arriving tomorrow. You probably have one brother.

[Mylanguageclick]

I agree.

[SoothingDave]

I personally think such attempts to determine how many brothers someone has through his use of commas is folly.

[Raymott]

I personally think such attempts to determine how many brothers someone has through his use of commas is folly.

It would be folly if the point of the exercise went no further than determining the number of siblings.