I’ve had a Realm for several months, built using the official City Texture Pack from the store. After updating to 1.13.0, every time I load my realm, it also loads in a texture pack called ‘PureBDcraft 128x v1.7.0’. 
I have never purchased this pack so don’t know why it shows up. It lists this pack, plus the City Texture Pack as both being active. If I deactivate the PureBD pack, then load the Realm, it still has the PureBD textures applied, and if I look in the settings menu, it’s right back there in the resource pack list. If I click ‘view in store’ on PureBD pack in the resource pack menu, it actually takes me to the City Pack on the store.

This issue only effects my world if it is a Realm. If I download it, then the City Pack loads as normal, and the PureDB pack never appears. 
I have the exact same issue on my iPhone 11 Pro Max (iOS 13.2). I have deleted and reinstalled the apps, but it didn’t fix the issue. It appears as if both of these texture packs have the same identifier code when working with Realms, so it pulls both of them at the same time. Even if I change the order so the City Pack is at the top of the list, the PureBD pack still shows in game. There’s no way for me to use the City Pack in my realm.