Is it possible to unlock an iPhone without knowing passcode?

I'm very sorry for your loss. It would have helped if you had started with that sad news. See this link to request help from Apple --> How to request access to a deceased family member's Apple accounts - Apple Support

Did you forget the passcode or did you purchase a used iPhone?

If you have forgotten the passcode, but you know the Apple ID and Passcode used to set up the device, you can erase the device using your home computer by following the directions in this link --> If you forgot the passcode on your iPhone, or your iPhone is disabled - Apple Support

If you have purchased a used iPhone and you don't know the Passcode, Apple ID or Apple ID Password used to set up the phone, you've wasted your money. Apple won't unlock such a phone. We can't help you unlock such a phone. In a situation such as this, either get your money back or recycle the phone responsibly.

Restoring a device may work, but if its IC locked and you dont got the details, device is bricked

You're welcome and again, I'm so sorry for your loss.