Hey FiraB,
Do you share an Apple ID? Check under Settings and then the name at the top. When tapping it, you'll see the Apple ID email address in use. If you are sharing an ID, this is expected, and we'd recommend one of you creating or signing out of and then into your own Apple ID to stop that behavior.
If you're using the same Apple ID for sharing purchases or subscriptions, Family Sharing allows you both to have your own accounts while still maintaining purchase sharing if you wish. See more info here:
Let us know if that helps.
Cheers!