Yes, every Superannuation Trust must have a Trustee. This is because the law requires that for a Trust (an SMSF is a Trust) to exist there must firstly be some Trust property and secondly, it is the Trustee (or Trustees) who hold the Trust property on Trust for a Beneficiary or Beneficiaries (there must be a separation between the legal and equitable ownership). A Trust is not considered a legal entity.
In the case of Superannuation Trust the Superannuation Laws requires that a Superannuation Trust must have a Trustee.
All the Members must be Trustees if the Trustees are individuals (except in the case of Members who are not eligible to be Trustees i.e. minors, bankrupt, unsound mind, then an authorised representative would be appointed) and if the Trustee is a company then all of the Members must be the directors of the Trustee Company where eligible.
If there is only one member then there must be 2 Trustees if the Trustees are individuals. The Trustee who is not the member can be a relative of the member only if they are the employer of the Member or a non-relative of the member if they are not their employer.
If there is only one member and the Trustee is a company then the Trustee company can be a single member company of which the member is the sole director or it can be a two Director company whereby the second Director is a relative of the member only if they are the employer of the Member or a non-relative of the member if they are not their employer.