A non-banking financial company (NBFC) is a company registered under the Companies Act, 1956 and is engaged in the business of loans and advances, acquisition of shares/stock/bonds/debentures/securities issued by government or local authority or other securities of like marketable nature, leasing, hire-purchase, insurance business, chit business, but does not include any institution whose principal business is that of agriculture activity, industrial activity, sale/purchase/construction of immovable property.
So for a NBFC co is merely engaged in business of giving taking loans and advances for all corporates.
In your case merely investing in shares of subsidiary co does not fall under the NBFC head.because A non-banking institution which is a company and which has its principal business of receiving deposits under any scheme or arrangement or any other manner, or lending in any manner is also a non-banking financial company (residuary non-banking company).
and your comapany does not registered as a NBFC but as a traspotation co.