iPhone Face ID also Unlocking for my Brothers Face, Why?

I have bought brand new iphone 11 about 1.5 years ago
I have only one face id but that face id is opening when my brother shows his face
How to fix it . Is ther any solution

Hi Bro,

As a basic troubleshooting step, remove the existing face id setup and again configure your face id. Then immediately try unlocking it with your brothers face.

Usually, within our family when we have same facial features and structure, face id could be unlocking. But if the same happens for any of your friends or other family members, then it could be defective. Visiting apple service center and getting it diagnosed is recommended for any faults.

I hope it helps.