Can two gst, two businesses exist in same premises?

Hello all,

We run a food business. We would like to sell our food through existing restaurants. Suppose Restaurant "A" is already in a location with proper GST and all other compliance. Now, we, Restaurant "B" would like shake hands with "A" and start selling our items under different name, GST etc in the same shared location. Is it legally allowed? What happens in the following scenarios..

1. If the owner of the restaurant "A" wants to own both A and B, can he have different GST for both the brands?

2. If "A" is owned by X and can B be run by Y where as both X and Y enter in to a sublease agreement? 

3. If "B" wants to sell only few products through "A", what agreement he has to have to ensure he gets what he sells thr' "A" with different branding of "B" ?

Thanks in advance!

Vin.