Q: My husband and I each have iPhone 4’s, from different providers (his is provided through his job). Whenever I set a reminder in my phone, it shows up on his phone. How can we correct this?
A: It sounds like you’re sharing the same iCloud account on both of your devices, which essentially means that you’re sharing the same Reminders list, and possibly other iCloud related information as well such as Calendars and Contacts.
If you only use reminders on your iPhone and do not need to access them from another device such as an iPad or computer, you can simply turn Reminders OFF by going to Settings, iCloud and toggling off the “Reminders” switch.
By doing this, your Reminders will only be stored locally on your iPhone and will not be synced to your iCloud account, and therefore not to your husband’s device. Alternatively, if your husband doesn’t use Reminders, or uses them but doesn’t need them on multiple devices, you can simply toggle off his iCloud Reminders setting to prevent him from receiving your Reminders.
Ideally, however, you should set up separate iCloud accounts for each of your devices—at least for some of your data such as Reminders. Normally, with entirely separate iCloud accounts, you will each have your own set of Calendars, Reminders, Contacts, Safari Bookmarks and Reading List, Photo Stream, Documents & Data, and iCloud Backups. Note that with separate accounts, however, you also each get your own separate 5 GB of iCloud storage for backups, Mail, and Documents & Data.
If you still want to share some of your data between devices—such as having a common Photo Stream, for example—you can continue to share a single primary iCloud account while configuring a second, personal iCloud account on each of your devices for your own personal data. Keep in mind that some iCloud features—Safari Bookmarks & Reading List, Photo Stream, Documents & Data, Backups, and Find My iPhone—can only be enabled on the primary iCloud account on your device. Mail, Contacts, Calendars, Reminders, and Notes can be enabled on a secondary iCloud account, however, and in fact you can even enable these on more than one iCloud account.
So if you still want to share a Photo Stream, or keep your devices listed under a single Find My iPhone account, you can do this by leaving your primary iCloud account configured as-is, and then creating a second iCloud account for your personal contact, calendar and reminder data.
To do this, first migrate your contact, calendar and reminder data to your local iPhone by turning OFF each of these services on the primary account. This will offer you the option to create a local copy of the data that you’re currently syncing with iCloud. This local data will later be automatically uploaded to your new iCloud account when you enable these features there.
To create a new iCloud account, go to Mail, Contacts, Calendars in your iOS Settings app, and add a new account, choosing “iCloud” as the account type. You can either enter the Apple ID and password for an existing account here, or create a new one directly from this screen if you haven’t done so already.