@Mike_IU5HES 

Hi,
If your cameras and the cameras in your mother's house are bound to different accounts, it's unable to have two accounts in the Tapo app at the same time, but you can log out from one account and then log in with a different account to manage the different cameras.

Or you can log in to the account that manages the cameras in your mother's house, then share the cameras with your account, and then you can watch all the cameras after logging in to the Tapo app with your account. 
How to share your Tapo smart devices with your families?

Best Regards