He has been to New York, in which his brother studies at a college.

[wotcha]

"He has been to New York, in which his brother studies at a college."


Is the above sentence grammatical?

I mean is it ok to put a comma before a preposition and a relative pronoun?

 

[probus]

There are no universally accepted rules about the use of commas. The style manuals of highly respected journals have various rules.

For myself, I would use the comma in your example, but I would say where rather than in which. Also, you should use the present continuous tense is studying rather than the simple present studies.

 

[Raymott]

There are no universally accepted rules about the use of commas. The style manuals of highly respected journals have various rules.

I have to disagree about your first sentence here on a technicality. There are some universally accepted rules, but there is no one collection of rules which is accepted universally.

"He has been to New York, where his brother studies at a college."
In this case, I'd say the comma is mandatory. Are there any style manuals that don't suggest a comma before a non-defining clause?
"He has been to a city where his brother studies at a college." Does anyone suggest a comma before a defining clause?

I thought this rule was close enough to being universal.