Are you sharing an Apple ID instead of having separate ones?
initially the same but i created a seperate one. but we are still using the home sharing on itunes.
Go to your messages in setting and see what the receive and send numbers are. I had this problem to. It was because there was more than one number check as send and receive messages.
Maybe if you're both using the same iCloud ID, then you should turn that off for iMessage and only use your cell numbers for iMessage. Obviously if you're both using the same iCloud ID then you would both get the same messages.
Check in the Settings app... Messages > Send & Recieve
Then under "You can be reached at:" uncheck all except your cell number.
People can now only reach you for iMessages (and text messages) using your cell number, not your iCloud or AppleID.
Hope it helps.