Yes, a member can be considered to have a "legal disability" (excluding being under 18), provided that the legal personal representative of the disabled member is a trustee of the fund, or if the member lacks a legal personal representative, a parent or guardian of the disabled member acts as a trustee.
If the trustee is a company, the legal personal representative of the disabled member, or in the absence of one, a parent or guardian of the disabled member, must serve as a director of the company in place of the member.