An idea for Brat:

Are they a bonded pair? Star would suffer from separation?

Or Brat is Star's companion. We all know that cats need other cats to help keep themselves clean and healthy (such as cleaning the ears, playing games, and mental health).

Hope you are successful. Cats are far more useful than people realize. Mine alert me to guests before I hear them coming up the walk. They also let me know when I'm not well, such as blood sugar or blood pressure.