(1) a conservator may represent and bind the protected person whose estate the conservator controls;
(2) a guardian may represent and bind the ward if a conservator of the ward's estate has not been appointed;
(3) an agent having authority to act with respect to the particular question or dispute may represent and bind the principal;
(4) a trustee may represent and bind the beneficiaries of the trust;
(5) a personal representative of a decedent's estate may represent and bind persons interested in the estate; and
(6) a parent may represent and bind the parent's minor or unborn child if a conservator or guardian for the child has not been appointed.