S.D. Codified Laws § 29A-5-106
Custody of a child may be sought by a person other than the parent under this chapter and the substantive law of this state. A person other than the parent may not use this chapter to seek custody if a proceeding is pending pursuant to chapter 25-3, 25-4, 25-5A, 25-6, 25-8, 26-7A, 26-8A, 26-8B, or 26-8C, or if the child is subject to the continuing jurisdiction of another court. Nothing in this chapter affects the provisions of chapters 25-4, 25-5, 25-5A, 25-6, 25-8, 26-7A, 26-8A, 26-8B, and 26-8C relating to the appointment of guardians and conservators and the administration of guardianships and conservatorships for children who have been adjudicated to be delinquent, abused, neglected, or in need of supervision. Nor may anything in this chapter affect the provisions of Title 27A, relating to individuals with mental illnesses. In the event of any inconsistency or conflict, the provisions of chapters 25-4, 25-5, 25-5A, 25-6, 25-8, 26-7A, 26-8A, 26-8B, and 26-8C or of Title 27A shall control, and the provisions of this chapter are in all respects to be supplementary thereto. A petition pursuant to this chapter seeking custody by a person other than the parent shall be dismissed if an action concerning the child is filed pursuant to chapter 26-7A, 26-8A, 26-8B, or 26-8C. If, while a guardianship petition pursuant to this chapter seeking custody by a person other than the parent is pending, an action is commenced pursuant to chapter 25-4, 25-5, 25-5A, 25-6, or 25-8, the court may, in its discretion, dismiss the guardianship proceeding and defer the child custody matter to the other proceeding or considering the stage of the proceedings, judicial economy, and best interests of the child, retain jurisdiction and establish the guardianship, or enter an appropriate protection order pending resolution of the pending proceedings.
SDCL 29A-5-106