Two siblings can adopt a child together in many states, but whether siblings can adopt a child together through a single joint petition depends on where you live. Roughly half the states and the District of Columbia explicitly allow two unmarried adults to file jointly. Others limit joint petitions to married couples, and the rest sit in a gray zone where the outcome depends on the judge. If a joint petition isn’t available in your state, a two-step second-parent adoption usually gets both siblings to the same legal destination.
Does Your State Allow Two Unmarried Adults to Petition Jointly
This is the gatekeeping question, and it has nothing to do with whether you’d be good parents. About two dozen states and D.C. explicitly permit joint or second-parent adoption by unmarried individuals. A handful expressly prohibit it. The rest are unclear, which in practice means some county judges will grant the petition and others won’t.
States that restrict joint adoption to married couples generally do so through statutory language limiting joint petitions to a “husband and wife” or requiring a “legally valid and binding marriage.” Two siblings walking into one of those courts with a joint petition will be turned away at the threshold. The rule is categorical. It isn’t about the quality of your home, your income, or your relationship with the child.
Before you pay for a home study or retain counsel, confirm where your state lands. A family law attorney in your county can answer this in a single consultation, and it’s the most important early expense in the process.
The Two-Step Workaround: Second-Parent Adoption
If your state won’t accept a joint petition from unmarried co-petitioners, the standard route is sequential. One sibling files alone and becomes the child’s sole legal parent. After that adoption is finalized, the second sibling files a separate second-parent adoption petition. A second-parent adoption lets someone adopt a child without terminating the existing legal parent’s rights, so the first sibling keeps full parental status while the second gains it.
This route costs more and takes longer. You pay two sets of filing fees and may need two home studies. But both siblings end up with the same legal rights: medical and educational decision-making, inheritance in both directions, and standing to act for the child in every setting. In states where the law on joint petitions is unclear, some attorneys will file jointly and let the judge decide; others recommend the two-step path to avoid a denial.
Eligibility Requirements for Both Siblings
Age requirements vary. Seven states set the minimum at 18, a few require 21 or 25, and many don’t specify a minimum beyond legal adulthood. Some states add an age-gap rule, typically requiring the adoptive parent to be at least 10 years older than the child. For siblings adopting a younger relative, this usually isn’t a problem, but it can matter when the adopting siblings are close in age to the child.
Beyond age, courts look at whether each petitioner can provide a stable home: steady income, adequate space, physical and mental health sufficient for parenting, and a clean background. Both siblings generally need to live in the same household, because the court wants the child to have one consistent home rather than two addresses to shuttle between. A felony conviction, a history of child abuse or neglect, or a serious untreated substance problem on either sibling’s record will likely sink the petition regardless of how strong the other sibling looks on paper.
Consents the Court Will Require
An adoption cannot proceed without the consent of the child’s legal parents, unless a court has already terminated their rights. This is the consent that carries the most legal weight, and any defect in obtaining it can unravel the adoption years later. Both biological parents must sign a formal written consent, usually before a judge or notary, giving up all rights permanently.
The Child’s Consent
Most states require the child’s own consent once they reach a certain age, usually between 10 and 14. The most common threshold is 12, used by roughly two dozen states; another large group sets it at 14. A few states require it as young as 10. Courts can sometimes waive the requirement if the child lacks capacity or if the judge finds waiver in the child’s best interest, but a child old enough to have an opinion will generally be heard.
Foster Care and Putative Fathers
When the child is in foster care, the public agency with custody must also consent and provide a written placement recommendation. Agency involvement usually means the biological parents’ rights have already been terminated through a separate proceeding, which simplifies the consent picture.
If the child was born outside marriage, the adoption may also require a check of the state’s putative father registry. These registries let men who believe they may have fathered a child register to receive notice of any adoption proceeding. A registered potential father must be notified and given a chance to object. If he didn’t register within the state’s deadline, most states treat that as implied consent and allow his rights to be terminated without his agreement. Missing this step is one of the faster ways to have a finalized adoption challenged later.
Indian Child Welfare Act
If the child is or may be a member of a federally recognized Indian tribe, the Indian Child Welfare Act imposes requirements that override standard state procedures. The party seeking the adoption must notify the child’s tribe and any known parent or Indian custodian by registered mail with return receipt requested. No termination of parental rights or adoption can move forward until at least 10 days after the tribe receives notice, and the tribe can request an additional 20 days.1Office of the Law Revision Counsel. 25 USC 1912 – Pending Court Proceedings
ICWA also sets a strict preference order for adoptive placements of Indian children: first a member of the child’s extended family, then other members of the child’s tribe, then other Indian families. The tribe can set a different order by resolution, and the court must follow it.2Office of the Law Revision Counsel. 25 USC 1915 – Placement of Indian Children Siblings adopting a younger relative with tribal heritage actually benefit from these preferences as extended family. Failing to follow ICWA’s procedural requirements, however, can void an otherwise completed adoption.
The Home Study
The home study is the most involved part of the process and the piece that makes or breaks most adoptions. A licensed social worker visits the home, interviews each sibling separately and together, reviews financial documents like tax returns and pay stubs, and assesses whether the household is safe and appropriate for a child. They look at everything from smoke detectors and sleeping arrangements to how the siblings communicate and handle conflict.
Both siblings need a recent physical, usually within the past 12 months. Every adult in the household goes through a criminal background check, including fingerprinting and a search of child abuse and neglect registries. The whole process typically takes three to six months and produces a written report with a recommendation to the court.
Private agencies or independent social workers generally charge between $1,000 and $3,000 for a home study. If you’re adopting from foster care, the cost is often reduced or waived. A completed home study has a shelf life, so if your case drags, you may need to pay for an update, and an expired study can push finalization back by months.
Filing, Supervision, and Finalization
The petition is filed in the family court in the county where you live or where the child resides. It names both siblings as petitioners, describes the child’s current legal status, and states the legal basis for the adoption. Filing fees vary by jurisdiction but generally run in the low hundreds. Many courts accept electronic filing.
The judge will often appoint a guardian ad litem to represent the child’s interests independently. The guardian ad litem acts as a factfinder, visits the home, interviews the siblings, and may talk to the child depending on age. Their written recommendation carries real weight.
After the child is placed in your home but before the adoption is legally final, most courts require a post-placement supervision period of roughly three to nine months. A caseworker visits monthly to observe how the family is adjusting. The finalization hearing itself is usually short. Once the judge signs the decree, both siblings become the child’s legal parents, the court issues a new birth certificate listing both as parents, and the child’s legal ties to any prior parents are permanently severed.
The Adoption Tax Credit When Two Siblings Adopt
The federal adoption tax credit for 2026 covers up to $17,670 in qualified adoption expenses per child, with up to $5,120 of that amount refundable even if you owe no federal income tax.3Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 Qualified expenses include attorney fees, court costs, travel, and the home study fee. For 2025, the credit phased out at a modified adjusted gross income of $259,191 and vanished above $299,190; the 2026 thresholds adjust slightly upward.4Internal Revenue Service. Adoption Credit
Here’s the piece that specifically affects two unmarried siblings adopting together: the $17,670 limit applies once per child, not once per petitioner. The two of you must divide the credit between your separate tax returns, but you can split it any way you agree on.5Internal Revenue Service. Instructions for Form 8839 One sibling might claim all of it if the other has little tax liability, or you can split evenly. The IRS does not mandate a ratio.
If you’re adopting a child from foster care who has been determined to have special needs, you may also qualify for Title IV-E adoption assistance: monthly subsidy payments and automatic Medicaid eligibility for the child, with no income test for the adoptive family. When a relative adopts, the usual requirement to show the agency first tried to place the child without a subsidy is waived, which makes qualifying somewhat easier for sibling adoptions of younger relatives in foster care.
What Both Siblings Hold After the Decree Is Signed
Once finalized, both siblings have the same legal status as biological parents. The child gains full inheritance rights from both adoptive parents, and both parents can pass property to the child through intestate succession. In most states, the adoption simultaneously severs the child’s legal right to inherit from biological parents, though some states carve out exceptions when a close relative adopts.
An adopted child is eligible for Social Security survivor benefits if an adoptive parent dies, provided the parent worked long enough to qualify.6Social Security Administration. Benefits for Children Both siblings also gain standing to make medical decisions, enroll the child in school, add the child to employer health insurance, and apply for a passport on the child’s behalf.
One point worth being clear about before you file: adoption is permanent. If the siblings later fall out or one wants to step back from the parenting role, that requires its own legal proceeding. Parental rights don’t dissolve just because the co-parenting relationship does.