(a) Unless the managing conservator is the petitioner, the written consent of a managing conservator to the adoption must be filed. The court may waive the requirement of consent by the managing conservator if the court finds that the consent is being refused or has been revoked without good cause. A hearing on the issue of consent shall be conducted by the court without a jury.
(b) If a parent of the child is presently the spouse of the petitioner, that parent must join in the petition for adoption and further consent of that parent is not required.
(c) A child 12 years of age or older must consent to the adoption in writing or in court. The court may waive this requirement if it would serve the child's best interest.