When looking at iCloud prefs you can see that Notes has its own checkbox but Reminders is paired with the Calendar checkbox. My wife and I share my Calendar via my iCloud ID, but we would love to have separate Reminders iCloud sync, one to a 24 inch iMac in the kitchen and the other to a 27 inch iMac in the office but this can't be done without losing the common Calendar. Really silly and iCloud still isn't flexible enough for an active family that wants to share some data among devices but not all.