Australia Share holding and Business Structure Setup

[Saru]

Hi ,Our director has a trust and hold shares of two companies for eg. A & B in NSW Australia. he is a sole director and holds 100% shares in both companies and thus the two companies are associated. Now he is intending to become a share holder of another company (C )where he will hold approx 30% shares. Do A, B &C become associated companies if the director buys shares using the same trust. if yes, what is the best way to proceed with this. Do we have to set up another trust and trustee?