About relatives pronoun with BeV

I have a question about this sentence:

• The guy who is my brother is playing the piano.

Is it okay to remove "who is" and turn it into this?

• The guy my brother is playing the piano.

I wanna make sure when the relative pronoun and beV are together, is it okay to remove them under any of circumstances except for being behind a comma?

Thanks!

Solution 1:

No, you can't always remove WHIZ - your second sentence is barely grammatical for me: I can only read it as my brother in apposition, normally preceded by a comma.

You can drop the WHIZ before a participle (present or past), or a prepositional phrase, but not normally anything else. See https://www.grammarwiz.com/reduced-relative-clauses.html