If you want them all to have the same address's and stay in sync then they must all use the same iCloud account.
To be clear, with your devices connected and selected in iTunes, you went to the Info pane for each device (iPhone and iPad) and turned off contact/calendar, and any other syncing? This has to be done for both devices.
You also need to have your computer syncing to iCloud. This is done in System Preference for a Mac. There is something called the iCloud Control Panel for a PC (Vista or nor newer).
http://www.apple.com/icloud/setup/
If so, try this.
Go to icloud.com from your computer browser. See if your contacts are doubled there. If they are:
Turn off your calendar syncing on your iPhone and iPad in the iCloud settings. When it asks if you want to delete the contacts off your devices, say yes.
Delete all duplicates, either at icloud.com or on the computer, and confirm that the changes have synced back to the other.
Once that has been done and seems to work (you can try making changes and see if they sync), go ahead and turn the contacts back on for each device.