Hi
If the Apple Watch is locked by a passcode and your brother cannot unlock it via the normal procedure, then follow these steps to erase it and re-pair it:
- Connect the watch to its charging cable, with power connected.
- Press and hold the side button until you see the Power Off slider.
- Press firmly on the display (do not try to slide the Power Off slider - just press down more firmly than a normal tap) and then tap on Erase all content and settings.
- Re-pair the watch using the Watch app, choosing to Restore from Backup if offered the option.
More information:
Set up your Apple Watch - Apple Support
If you forgot the passcode for your Apple Watch - Apple Support
If you are instead referring to Activation Lock, which prevents unauthorised use of Apple Watch if it is lost or stolen, then:
If the watch is locked to your brother's own account, but he is having issues with his credentials:
- It may help to follow the instructions here:
If the Apple Watch is pre-owned and locked to the previous owner's account:
- Your brother will need the previous owner (who may not be the seller) to either enter their Apple ID and password on your iPhone or to turn the feature off via https://www.icloud.com/ (by signing in with their Apple ID > Find My iPhone > select the Apple Watch > Erase Apple Watch > Next until erased > click X next to the watch).
- If he cannot arrange for the previous owner to do this, he should return the watch for a refund.
- He will not otherwise be able to use the watch. There is no way around this security feature.
More information:
About Activation Lock on your Apple Watch - Apple Support