Hello shafi144,
Thanks for reaching out to Apple Support Communities. I understand that your brother's name is showing on your iPhone. I'm happy to help you find some information.
First, make sure your name is associated with the iPhone. Here is a resource that can assist you:
Change the name of your iPhone, iPad, or iPod using your computer
Next, make sure you are signed in with your Apple ID.
Sign out of iCloud on your iPhone, iPad, iPod touch, Apple TV, or Mac
Sign in with your Apple ID
If you have any issues after reviewing the links, please let me know.
Have a great day!