It is an ATO requirement to have a minimum of 2 Individual Trustees or a Corporate Trustee. Note the second Trustee does not need to be a Member. However, the second Trustee can be a Member if you so decide. A Trustee should have a Tax File Number and be over 18.

In a Corporate Trustee structure, all Members must be Directors of the Corporate Trustee.

The term “settlor” refers to the person who establishes a Trust. In an SMSF, the settlor is the Trustee.

Clink here for more information on the ATO requirement