iPhone 5c getting Texts from another iPhone 5c. Why???

I recently got my parents, each, an iPhone 5c. At first I was going to make them share an iTunes account, because they really don't know how to use it anyway and they hate putting passwords everywhere. Eventually, I set up a 2nd iTunes account for the 2nd phone. I went through, the mail, imessage, facetime and all the apps needed to change the information.

For some reason when ever my mom sends a text message or recieves it, it also shows up on my dad's phone! But it doesn't happen visaversa. I checked the imessage info and it's correct, just his itunes and his phone number. This just happens to my dad's cell, and they are only my mom's text messages. How do I turn this off/disconnect what is going on?

Please help, thanks!