How to remove activation lock from an Apple device (watch) that was inherited from a recently deceased family member?

We can unlock his phone but do not know his Apple ID login information. We have removed the device from his Apple ID and unpaired the watch from his phone, but we are not able to pair it with a new phone. I think normally we would need to log in on Apple.com and remove the device and the lock but we’re not able to do so. Wondering if there’s any other way to make it work.