Removing deceased's iCloud account from iPhone

For information about how to request access to a deceased family member's Apple account data, and possibly their equipment, read this support article --> How to request access to a deceased family member’s Apple Account - Apple Support

Apple says:

"While we may also be able to help remove Activation Lock from devices that use your loved one’s original Apple ID, their iPhone, iPod, and iPad will need to be restored to factory settings before they can be used with another Apple ID. Please note that devices locked with a passcode are protected by passcode encryption, and Apple can't help remove the passcode lock without erasing the device."

"For security, Apple requires and verifies legal documentation before we can assist with a deceased person’s account. This generally includes a death certificate, and may also require a court order or other documentation. The requirements vary by country and region. We have great sympathy for surviving family members and try to help with requests as much and as quickly as possible."