comma necessary?

Hi tanguatlay
I would use the commas, but I am not an English expert. You should wait until someone who has a better understanding of the English language comes along.

The commas are neccessary. The phrase "whose father is a lawyer" is a parenthetical phrase, which means that it interrupts the sentence "John is my best friend" in order to add information about John.

If the information contained in such a parenthetical phrase is not essential to the meaning of the phrase, it is set off by commas. If not, no commas should be used:

John who saved my life is my best friend.

An article about commas is to be found at

http://en.wikipedia.org/wiki/Comma_(punctuation)

great advice, my native language is spanish, and even in spanish commas are necessary in examples like this...

I wrote this

If the information contained in such a parenthetical phrase is not essential to the meaning of the phrase, it is set off by commas.

I should have written this

If the information contained in such a parenthetical phrase is not essential to the meaning of the sentence, it is set off by commas.

The comma is required as "John is my best friend" could stand on its own and the remainder expresses another thought.