Because the priority of the family is the data (photographs) there is one possibility. If they can provide sufficient documentation to satisfy Apple the family member can try to get control of the Apple ID account.
https://support.apple.com/en-us/HT208510
If they can get sufficient documentation to satisfy Apple's policy then the family can check iCloud (www.icloud.com) on a computer to see if the photos are there. I do not know if this applies in your country though.
With the Apple ID account in their control the person's iPhone can be erased, but if the photographs do not exist in their iCloud and only exist in the iPhone they cannot be recovered without the screen code. However, if the relative though had an iCloud backup of their iPhone, this could be restored.
There is no way to know until the Apple ID is under their control.