How to unlock a deceased Family member's iPhone

This was my brother's phone. He died in an accident. As much information as I have about this phone, I have added that only. It has been 3 years since I bought it. I don't have the bill for it. My brother knew from where he bought it. There was a bill for that only. I had the information about that only. He died in an accident. My brother did not have complete information about it. As much as I knew, I have added that much. For location and proof, ID, PAN Card, Aadhar Card is with me. Please help. I don't have the bill for it. Please help.

[Edited by Moderator]