I work in IT and if backup isn't automatic things are going to get lost. Trying to sync up multiple manual backups really isn't a good way to go. I used to keep a copy of photos on my computer, my wife's, and an external drive. I had a hard drive failure and when I went to recover them from my external drive I found out it had failed as well. I copied them over from my wife's computer. I later discovered not everything had been on my wife's laptop. The originals from our honeymoon in Paris were gone. I have some low res copies of them but not the originals. I have used Google Drive for a couple of years now. It's $2 a month for 100GB. All my photos go right into my Google Drive which is then automatically synced to the cloud and my wife's computer.
Amazon now offers unlimited photo storage for prime members. Unfortunately it's not automatic, you have to upload them. Since I was running out of space in my Google Drive I uploaded all my previous years photos to Amazon and I put my current year photos in Google Drive which is automatically backed up.
Microsoft OneDrive would also be a nice solution. They have plans for $2 a month for 100GB, $4 a month for 200GB, and $7 a month for 1TB which also includes Office 365. The nice thing about Google Drive and Microsoft OneDrive is you can have the files locally on your PC but also access them on your phone or from any other computer.