imessage not working with one person

[colettesaxby]

I can send imessages to everyone and they turn blue apart from my partner, they turn green when I send them to him. He also can send imessages to everyone and they turn blue but when he sends them to m they are green. Can anyone help? We are both using 5.1 on iphone 4

 

[ann713]

Might be a silly question, but are you both using the same Apple ID? I'm not sure if that's remotely possible for different phone numbers but...