If you read the fine-print on cloud-based storage/backup solutions, you'll likely find that they do not "guarantee" your data.
I knew someone whose online backup service had an outage and lost their data (so they couldn't do a restore). They were a bit shocked that they were paying for a backup service and... the only time they actually needed to do a restore, the data was gone. The vendor pointed out that the service level is merely "best effort" -- there is technically no "guarantee".
But there are other problems with online services. If you want your family to be able to access your photos long after you are gone ... first they have to be aware that you stored photos online somewhere, and they need to know where and how to get them (they need account credentials) and will they remember all this?
If not, you spent your whole life paying a fee to preserve data that will never be recovered.