My brother insists that I don't reveal his "secret identity" ... what do I do?

Don't reveal his secret identity, as of right now. Instead, try to gather some pertinent information, so you can decide who you might want to tell- medical professionals or the tabloids or even no-one, if applicable...

Ask him questions about what he does, and especially what he can do.

Does he believe he can climb walls or shoot webs out of his wrists?

Was he bitten by a spider and did it make him very sick and delusional for days or just itchy?

Did he have to buy his costume or did he weave it with his own spinnerettes?

What are his powers or is he just on a mission with technology (because if he is like Batman not Spiderman, that might be safer, since Batman always gets the proper safety equipment and uses the buddy system)

Is the Spiderman thing just a cover for another secret identity, like ScannerMan or the Nightstick?

Has he actually rescued anyone and would they be willing to give a testimonial about his heroism? After you know more, you will be able to decide for yourself. I try to always get along with my brother, even though mine has no super powers, I just love him and whatever he does that is safe and makes him happy is ok with me. So use your best judgement.

Is he for real? Does he actually go out and help people?

If so, let him do what he wants. He's probably not mentally ill, but a little obsessed with an image. He does probably overestimate his own abilities, and depending on the crimes he stops, may be putting himself in danger. But that's his own life, and his own prerogative.

And even if he doesn't, and it's all just a play, why "reveal his identity"? Would that even serve a purpose?

I suspect this question is a joke, but if it isn't, stop worrying about him.

Your brother needs some serious help and if you love him I would not dick around but go now and get him the help he needs. If you fail to act you just maybe either standing graveside at your brother funeral because he got killed doing something stupid to fulfill some juvenile fantasy or delusion. The second probability is he could end up in trouble with the law. So pick up the phone, call mom and dad or a mental health professional and get him some help fast!

Your brother desires severe help. Please do no longer permit him proceed in this way. He might get harm or killed by skill of entering right into a topic that he shouldn't. in case you care approximately him in any respect, urge him to get some help. he's somewhat blended up.

Spidey doesn't use a cape. Your brother is a pathetic wannabe.

lol wow 1st of all police scanners are illegal so he needs to be careful and 2nd he has no secret identity he's crazy its simple get him some help soon

I think he might have some issues...maybe he should see a psychiatrist? Trying to be a superhero is just plain weird...and especially at his age.

Reveal his identity at once...to a good local psychiatrist.

you should keep his identity secret. there is only one spider-man and he belongs in the movie for everyone to enjoy watching.

No. Report him to the nearest mental hospital.