Yes because you two are sharing the same apple id for imessage prob for facetime and icloud.
You can share the same apple id for musics and apps, but different id, for imessage/facetime and icloud.
Go to settings - message - send&receive - you can be reached at - hit the circl i next to the apple id - remove this email.
then whomever gets the new email go back there and then add the new apple id.