Hi ki297,
Welcome to Apple Support Communities. We understand that you're having an issue with with the Screen Time setting on your device. We'd like to help.
From what you've provided, it sounds like you've been unsuccessful working with your brother to resolve this issue. For Screen Time on your device, this security is set up on your device itself. Due to that, we're unable to remotely help with accessing your device or changing your password. The only way to remove that password requirement is to enter the details on your device or wipe device and set up as new.
Does your brother not remember their Apple ID and password? If that's the case, have them follow these steps to try to reset their password so they can help:
Reset your Apple ID password on your iPhone or other trusted Apple device
1. Go to Settings.
2. Tap your name > Password & Security > Change Password.
3. Follow the onscreen instructions to reset your password.

You can also follow this process on a trusted iPad, iPod touch, or Apple Watch.
Hope that helps.
Take care!