MATHIAS, J.
M.S. and C.S. lived together in a same-sex relationship for more than ten years. During the relationship, C.S. was artificially inseminated with donor semen and gave birth to a daughter, S.S., in 2003. In August 2007, M.S. and C.S. sought to establish a legal relationship between M.S. and S.S. by filing a “Joint Petition to Determine Custody.” In the petition, M.S. and C.S. agreed that they should have joint legal custody, with C.S. as the primary physical custodian, and that M.S. should have parenting time as agreed by the parties or, in the event that they could not agree, in accordance with the Indiana Parenting Time Guidelines. [Footnote omitted.] On September 5, 2007, the Bartholomew Superior Court entered an order providing for custody and parenting time as set forth in the petition.
On April 21, 2009, M.S. and C.S. ended their relationship after a heated argument during which M.S. physically attacked C.S. and threatened C.S.’s life in the presence of S.S. At a hearing held on May 4, 2009, the trial court concluded that it had had no legal basis to enter the September 5, 2007 order, and therefore voided the order without a request to do so by either party. . . . .
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M.S. first asserts that the “Joint Petition to Determine Custody” was properly filed under Indiana Code section 31-17-2-3, and that the resulting September 5, 2007 order was therefore properly entered and legally binding. . . . .
Indiana Code section 31-17-2-3 provides that a child custody proceeding is commenced by:
(1) a parent by filing a petition under IC 31-15-2-4, IC 31-15-3-4, or IC 31-16-2-3; or (2) a person other than a parent by filing a petition seeking a determination of custody of the child.
Here, however, C.S.’s and M.S.’s “Joint Petition to Determine Custody” sought to establish a shared custody arrangement. We conclude that under the terms of Indiana Code section 31-17-2-3, the General Assembly did not intend to allow parents to establish joint custody with third parties by simply filing a joint petition with a trial court, because to do so would allow parents and third parties to circumvent the requirements of the Adoption Act.
Adoption creates a parent-child relationship between individuals who would not otherwise share such a relationship. Stepparent adoption allows a stepparent to adopt the biological child of his or her spouse without divesting the spouse of parental rights to the child. Ind. Code § 31-19-15-2 (2008). This court has interpreted the stepparent adoption statute to allow a biological mother’s children to be legally adopted by her same-sex domestic partner without divesting the biological mother of her parental rights. In re Adoption of K.S.P., 804 N.E.2d 1253, 1260 (Ind. Ct. App. 2004); see also Mariga v. Flint, 822 N.E.2d 620, 626-28 (Ind. Ct. App. 2005), trans. denied.
The General Assembly has set forth specific procedural prerequisites to adoption in the Indiana Code. For example, for a child born out of wedlock, an adoption petition may be granted only if a written consent to the adoption has been executed by the mother and, under certain circumstances, the father. Ind. Code § 31-19-9-1(a)(2) (2008). [Footnote omitted.] It is well established that adoption statutes are in derogation of the common law and must therefore be strictly construed as to all procedural requirements. J.M. v. M.A., 928 N.E.2d 230, 236 (Ind. Ct. App. 2010); In re Petition of Gray, 425 N.E.2d 728, 730 (Ind. Ct. App. 1981).
Indiana Code section 31-17-2-3 and the adoption statutes cover the same general subject matter and must therefore be construed together. To permit C.S. and M.S. to use Indiana Code section 31-17-2-3 to create parental and custodial rights to S.S. simply by filing a joint petition to do so would circumvent the public policy behind, and the procedural requirements of, the adoption statutes. We conclude that Indiana Code section 31-17-2-3 does not contemplate the creation of a shared custody arrangement between a parent and a nonparent, regardless of the consent of the parties. The original entry of the September 5, 2007 order was therefore erroneous.
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Here, however, the entry of the September 5, 2007 order was no mere procedural error. Rather, as we noted above, the trial court lacked the authority to grant the joint petition under Indiana Code section 31-17-2-3 under any set of circumstances, and the error was therefore impossible to cure. We conclude that the September 5, 2007 order was void ab initio and without legal effect, and consequently remains vulnerable to C.S.’s collateral attack. . . . For all of these reasons, the trial court properly vacated the September 5, 2007 order.
BAKER, C.J., and NAJAM, J., concur.