How Can I Unlock My Brother's iPhone in an Emergency?

Unfortunately, there’s no way to bypass the iPhone passcode. If Touch ID or Face ID isn’t set up, or if the phone has been restarted or hasn’t been unlocked in a while, you’re stuck. Only the passcode will work in those cases.

You can also call Apple Support directly. They hear a lot of unusual requests like this, and while they may not help in every case, they have the tools to assist you appropriately. Just make sure to explain the urgency of your situation.

Your best bet might be to contact the police or an Apple Store directly. They may be able to help in emergency situations, but keep in mind that they'll need to verify your story.