I can’t open a new Apple ID

my brother bought a new phone

Contact the store / seller.

If he has bought a 'new' 2nd hand iPhone, he must contact the seller (hopefully it is the previous owner), otherwise you have been scammed.

Each Apple device is linked/associated with an Apple ID of the person who did the setup.

Activation Lock prevents anyone who is not the owner from using this iPhone.

To unlock the Phone, he need the Apple ID and password of the previous owner, that were used during set up.

So he has to contact the previous owner.

The previous owner has to read -> this Apple article: What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch -> What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

Then the previous owner has to remove the iPhone from his account, see this Apple article:

Check your Apple ID device list to see where you're signed in

Check your Apple ID device list to find where you're signed in - Apple Support

Then he can sign in with his own Apple ID.

See the following Apple articles:

Activation Lock for iPhone, iPad, and iPod touch

Activation Lock for iPhone, iPad, and iPod touch - Apple Support

How to remove Activation Lock -> How to remove Activation Lock – Apple Support (UK)

• If you need help removing Activation Lock and have proof of purchase documentation, you can start an Activation Lock support request.

Read this before buy a 2nd hand iPhone.

He can also contact Apple support for help, -> Get Support (apple.com)

He has to show proof of ownership of your product, provide all documentation showing your purchase of the device.

If he does not has additional proof of ownership, contact the reseller. They may be able to provide the original purchase document.

Once Apple receive his proof of ownership, Apple will further review his request and provide an update.

See also -> Keep your receipt after you buy an Apple device

Keep your receipt after you buy an Apple device – Apple Support (UK)

Ask your money back if possible, perhaps he has bought a stolen iPhone.

OK,

Thank you for your feedback.

His Apple ID is the personal account you use with all Apple products and services. It includes the email address and password you use to sign in, as well as the contact, payment, and security details that you use with Apple.

He can’t merge multiple Apple ID accounts.

See -> Sign in with your Apple ID -> Sign in with your Apple ID - Apple Support

See also -> How to create a new Apple ID -> How to create a new Apple ID – Apple Support (UK)

Get more support and assistance see -> Contact Apple for help with Apple ID account security

Contact Apple for help with Apple ID account security - Apple Support