Wyo. Stat. § 14-2-310: Parties authorized to file petition.

(a) The petition for the termination of the parent-child relationship shall be filed with the court by:

(i) Either parent, when termination of the parent-child legal relationship is sought with respect to the other parent; or

(ii) The guardian or the legal custodian of the child; or

(iii) An authorized agency.

(b) The petition for the termination of the parent-child relationship may be filed with the court by a biological or adoptive grandparent acting in loco parentis to the child, where the child has resided with the grandparent for a period of not less than one (1) year and the placement is not under the direction of a juvenile court or the department of family services.