It's not supposed to work. Both Google and iCloud do the same thing in the same way. Choose which service you want to use and stick to that one.
What you're attempting to do is like having an email account from Yahoo and one from Gmail and then wanting them both to contain exactly the same messages and mailboxes. It just doesn't work like that.
Either stick to one or use both but for separate purposes (e.g. Work and Home) but they'll remain independent.