Gst Reg. 2 firm

You can include the new business in the existing GST registration.

You can take a new registration on the same PAN also. Here both GST registration will be deemed different person

You can also take a registration on a different PAN also

You have all three option. But be cautious that of you want to continue new business on the same PAN until you take a new registration for it you will still be liable to pay GST on its supplies under old GST registration