You have lots of options, but be sure you also have multiple backups at home.

Free -
https://www.moneysavingexpert.com/shopping/free-online-storage/

https://www.techradar.com/news/the-best-cloud-storage
https://www.pcmag.com/roundup/306323/the-best-cloud-storage-providers-and-file-syncing-services
https://www.digitaltrends.com/computing/best-cloud-storage-services-compared/
https://www.zdnet.com/article/whats-the-best-cloud-storage-for-you/
https://www.1and1.com/digitalguide/server/tools/best-cloud-storage-providers/

https://www.howtogeek.com/310776/all-the-cloud-storage-services-that-offer-free-storage/
http://techcrunch.com/2015/04/04/the-cloud-could-be-your-best-security-bet/#.hj7qvs:qAVY
http://www.thesimpledollar.com/free-cloud-storage/

I have been shooting, and still have the photos, since I was nine. I have boxes and boxes of film shots w/ negatives. I'm 71 years old and currently culling with the help of family members (at my insistence). Never forget, the media changes, starting with large floppies (even though I didn't use them for photos, just docs). When CD's came out, I used them as backup, then DVD's were the best because larger data storage. I used cloud storage, Carbonite, for a while after it came out. Had some problems when they used compression software; although I do not know if they still do. I just recently converted all my CD and DVD's to straight data and do a "bank" backup. Using three USB drives, one being my working drive, one being a backup and one other drive kept unplugged and rarely used (once a month) as the "off site" backup. I like Microsoft One Drive for documents; however, not sure if it is compatible with Apple products. I share with thumb drives (Family) and drop box for work. My caution statement is make sure the site or software does not compress. Please excuse the wordiness.

I use two different services, one for backup storage, and another for family access. I use Backblaze for backup storage; they're currently backing up a little over twelve terabytes for me. I did have a pair of local drives fail, and it took less than a week to get it all back up and running like nothing had happened.

For sharing, I use flickr. I choose to share images there with the known universe, but you can restrict access if you choose to. The downside for flickr is they only accept jpegs.

Not offended or even puzzled - everyone has the option of doing what they wish with their data, even if they do it poorly. This remark comes up every time someone asks about cloud storage, and it’s usually followed by a string of misinformation. I used to spend paragraphs refuting the mistaken info. and explaining why cloud is the best way to keep an off-site DR copy of your data, if you have decent internet access. Not anymore. It’s like trying to convince someone to be vaccinated - waste of time. I will simply say that I am a career computer professional - started with IBM in 1965 and spent 25 years of my career specializing in data storage. Worked for the largest storage providers in the world - EMC, NetApp, Oracle, IBM, DDN, Isilon and even a global file system company that relied on the cloud for shared storage. Designed and helped install the fastest storage in the world for some of the largest supercomputers in existence, and my opinion is that a MAJOR cloud provider is the most secure way to keep a copy of your data. My DR copy of my valuable data resides in the Amazon S3 infrequent access cloud, and I sleep well knowing that the data I spent thousand of hours generating is safe and available no matter what happens to my computer, my storage, my home (or my city). You should do as you please.

There is a difference between simple storage and a good display site. A storage site is nothing but an external drive, period. A display site allows for complex presentation options. In particular, it should allow for a photo to be "saved" once, but to be displayed in more than 1 place on the site, or "collected" to those other places. For example, if you are on vacation and take a photo of a deer you might want to display it in a "Vacation" folder as well as a "Wildlife" folder. This prevents the amount of file space used to grow too fast.

I use Smugmug to display my photos.

👍👍
A lot of people think that "off-site" means they should store a disk at aunt Minnie's house or the local bank vault. While every little bit helps, that is not enough.

If aunt Minnie is local, you could run into the Paradise problem. In one of the wildfires a year or two ago the entire town burnt down. That would include the local bank vault.
If aunt Minnie is distant, the inconvenience of synchronizing the off-site copy would lead to gaps in coverage.

Cloud storage is not only off-site, it is widely duplicated and distributed so there is no single location to have a regional problem that would impact the storage.

Me too. Several things I like about Crash Plan.

(1) Crash Plan saves versions. So if something gets backed up, then you edit it and it gets saved again, the older one is still there so if you really screwed up the edit you can go back. Also, since it saves changed files, if a file gets corrupted, it's changed and a backup program will save it. If you restore it you get the corrupted file. But you can restore the one before it and get the uncorrupted file.

(2) Crash Plan will save your stuff to the cloud. But you can also set it up to simultaneously save your stuff to a local disk. If you want to restore a lot of stuff, you can restore it from the local disk and you won't be limited by your internet speed.

One other point. The OP specifically asked about cloud storage. I think cloud storage is an important part of a backup strategy. But due to bandwidth limitations, local storage is much more convenient than cloud storage. Due to professional maintenance, cloud storage is much safer than local storage. I think it's important to use both local storage and cloud storage. Local for convenience and cloud for safety.

I think the issues have been noted already. “Backup” is just that. All your files are stored and secure. With something like Crash Plan, it happens automatically from your computer or when you connect external hard drives. You can store unlimited data, which means unlimited. You describe having a large set of data, and files you do not want lost. Good to send that to cloud backup. But with “backup” that data is not “accessible.” It is not designed to share or access at a moments notice. It can take months to recover your data - but with Crash Plan and some others, that data will always be there. Online “storage” is where you will send more limited data that is accessible to you and your family, and you can access it easily and quickly. Last I checked, Backblaze is a file backup system at an inexpensive price, though you have to update the files you have stored regularly - or it will delete “old” files. YouTube has a number of reviews on all the systems. Give us an update on what you discover and what seems
the most workable.

You have lots of options, but be sure you also have multiple backups at home.

Free -
https://www.moneysavingexpert.com/shopping/free-online-storage/

https://www.techradar.com/news/the-best-cloud-storage
https://www.pcmag.com/roundup/306323/the-best-cloud-storage-providers-and-file-syncing-services
https://www.digitaltrends.com/computing/best-cloud-storage-services-compared/
https://www.zdnet.com/article/whats-the-best-cloud-storage-for-you/
https://www.1and1.com/digitalguide/server/tools/best-cloud-storage-providers/

https://www.howtogeek.com/310776/all-the-cloud-storage-services-that-offer-free-storage/
http://techcrunch.com/2015/04/04/the-cloud-could-be-your-best-security-bet/#.hj7qvs:qAVY
http://www.thesimpledollar.com/free-cloud-storage/