Started receiving copies of text messages sent on other phone after upgrading to iOS 7
You need to look in Settings &gt; Messages &gt; Send &amp; Receive &gt; You can be received by iMessage at... and also Start new conversations from.

It looks as though your Apple ID has become set to receive messages on both (all) devices.  Ensure that only the phones unique phone numbers and non-shared email address for Apple ID/iCloud accounts are included on each device.

For future consideration, note that iCloud/Apple ID accounts are free, and that on each device you log into iCloud services (like mail, calendars, imessage etc) separately from the App Store, so if you share an account for the purpose of sharing downloads (and I see no other reason to do so) then you should consider using that account for App Store usage only, and each have an individual iCloud account for all other functions, that way you won't ever cross contaminate each others stuff.