Wrong Apple ID

I have all iOS devices in my family set up to use the same Apple ID for iTunes store purchases. Aside from set, all 4 of us have individual apple IDs for our devices (used in iCloud). When I upgraded my wife's and my own iCloud storage plan, I was prompted for our main "iTunes Apple ID" each time, to confirm the purchase. The purchase went through without a hitch. However, when I'm trying to upgrade my children's iCloud storage, the transaction prompts for their individual Apple ID, instead of the main one associated to the iTunes store. When I check the iTunes store set up (Settings>>iTunes and App Store) it shows the correct Apple ID and it normally prompts for that ID when purchases are made. For some strange reason however, when trying to upgrade the iCloud storage plan does it prompt for the device's Apple ID versus the "iTunes store Apple ID". Any ideas anyone????