Is there a way to gain access to a deceased family member’s iPhone and the data on it?

Start here: How to request access to a deceased family member's Apple account - Apple Support

Following the instructions in the document linked above, you can get access to his iCloud account. That will not allow you to bypass the Lock Screen passcode on the device, but will allow you to remove the activation lock. Hopefully, his data was synced and backed up to iCloud.