Exercising power of appropriation - does the second trustee have to be independent?

I am looking for views about appointing a second trustee before a sole executor can exercise their power of appropriation and whether that second trustee needs to be independent or can it be the executor’s brother.

I have an estate where the deceased’s Will leaves his estate equally to his adult son and daughter. The estate comprises the deceased’s 40% share of a property that he purchased with his daughter where they both lived before he died (tenants in common) and cash. The daughter is the executor and she and her brother have agreed that she will appropriate the 40% share of the property to herself and the equivalent amount in cash to her brother in part satisfaction of their respective interests in the estate.

The Will states that there be two trustees to exercise any powers (except for the power to appoint a second trustee which can be exercised by one trustee) and further, the 1st Edition of the STEP standard provisions apply which state that a trustee can benefit themselves provided there’s an Independent Trustee. The Will overrides the requirement to have the beneficiary’s consent to appropriate but I also know that the self dealing rule can be disapplied if the beneficiary consents to the appropriation.

In accordance with the Will, I will have to appoint a second trustee but given that the self dealing rule can be disapplied by the consent of the beneficiaries, does the second trustee have to be an independent trustee as per the standard provisions or can the beneficiary’s consent dispense with that requirement? It will be much easier if I can appoint the brother as the second trustee rather than having to find someone independent.