Currently Being ModeratedMar 24, 2013 1:47 PM (in response to khira.jaye)
If your Apple ID that you use for iTunes is the one you use in Messages then you will get this issue if that Apple ID is on his iPhone.
You or he will need to go to his iPhone > Settings > Messages > Send and Receive and remove Your Apple ID.
You may need to restart all devices but his Number should then disappear from your Messages app on the Mac.
He should be able to keep the Apple ID in the iTunes settings on the iPhone.
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.3)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad
"Limit the Logs to the Bits above Binary Images." No, Seriously