This is for my twin sister and I - we have decided to open our own business but are looking for a catchy name
Your business name should indicate what type of service that you are offering. Including your name will be great. Have a name that you can live with forever and that you can add other components to it.
Cause some trainers use their name but it's doesn't tell what type of business that you are offering.
Twin Stars Fitness (and Training if you offer the service) would be cool. Going off the fact you are twins. When someone asks why the name, you can tell them it's because your twins. It's fascinating.
You can do some whimsical decorations. Stars in logo. And inside.
There is a Twin Stars cartoon or sticker series. So you might have to write Twin Starz so you don't compete.
If you want a more "tougher" theme, you could go Twin Tigers or Twin Fitness Ninjas and have more orental theme decoration.