How to handle the case where multiple vendor names are actually all related together.

How to handle the case where multiple vendor names are actually all related together.

I have two suppliers sharing the same tax numbers in Canada and both belong to another supplier (holding) have the same tax numbers. There is a risk of paying several times the same invoice to different vendors or to deal with fraud.

How can we connect these companies among them and manage our PO's and our tinvoicess? Also, there is the management of supplier files that cause some headaches.