The siblingship gap: How DNA testing supports sibling and wider kinship care placements

For children entering the care system, few relationships matter more than those they share with their brothers and sisters.

Amid the upheaval of separation from parents, sibling bonds can offer a vital sense of identity, continuity and belonging.

Yet many children in care are still separated from their siblings, sometimes over considerable distances. Research from the Children’s Commissioner for England has found that an estimated 37% of children in care are living apart from at least one sibling, a disparity often referred to as the “siblingship gap”.

DNA testing has an important part to play in addressing this gap, in more than one way. It can help confirm that children believed to be brothers and sisters are, in fact, biologically related, supporting decisions to place them together.

It can also help confirm biological relationships more broadly, for example between a child and a potential aunt, uncle, or grandparent, allowing a wider network of family members to be considered as kinship carers in the first place.

Here, we look at how DNA testing can support sibling placements, and how it can also help unlock kinship care placements for the wider family.

Keeping brothers and sisters together

When children enter the care system, local authorities generally aim to place siblings together wherever possible, recognising the importance of these relationships to a child’s sense of identity and stability.

In practice, this isn’t always achieved, and the reasons are varied; from a lack of suitable placements to the individual needs of each child.

In some cases, though, the barrier is more fundamental; uncertainty over whether children believed to be siblings are, in fact, biologically related. This can happen where:

• A shared mother is confirmed, but the identity of one or both fathers is unclear, making it uncertain whether children are full siblings (sharing both parents) or half siblings (sharing only one)
• Family circumstances are complex, and testimonies about parentage are disputed or unverified
• A child’s birth certificate does not name a father, leaving that side of their biological family unconfirmed

These circumstances can complicate decisions about placing children together, particularly if a placement decision is challenged later, or if formal legal orders are being sought.

In these situations, sibling DNA testing can provide clarity. By analysing cheek swab DNA samples from the children involved and comparing these with DNA samples from a shared parent where available, it’s possible to establish whether children are full or half siblings with a high degree of confidence, helping social workers and local authorities make placement decisions based on evidence rather than assumption.

Proving kinship for wider family placements

While the siblingship gap relates specifically to brothers and sisters, a wider issue can affect other family members who come forward to care for a child.

Aunts, uncles, and grandparents are often considered as potential kinship carers but in some cases, the biological relationship between the carer and the child has never been formally established.

This is particularly common where a father is not named on a child’s birth certificate. If paternity has never been confirmed, this can create uncertainty not just about the child’s father, but about their wider paternal family, including any aunts, uncles, or grandparents on that side who may wish to be considered as carers.

This matters because the legal threshold for kinship care is high.

While a “think family” approach encourages local authorities to consider siblings and wider relatives as a first option for placement, the legal threshold for formalising kinship care is high. Under the Children Act 1989, a potential carer must generally be recognised as a “connected person”, such as a relative, to be considered for placement.

Where a biological relationship cannot be confirmed, a prospective carer may struggle to meet this threshold at all, even before an assessment process begins.

This becomes particularly significant during the Viability Assessment stage, which social workers use to determine whether a potential kinship carer should be explored further, and where a Special Guardianship Order (SGO) or Child Arrangements Order (CAO) is being sought.

If biological uncertainty exists, this can delay or even prevent a placement being considered, regardless of the strength of the relationship itself.

In these circumstances, DNA testing between a child and a potential aunt, uncle, or grandparent can help resolve that uncertainty early, giving social workers and legal professionals the evidence needed to move an assessment forward.

How complex relationship DNA testing works

Complex DNA relationship testing is used to determine whether a biological relationship exists between two or more people who are not a direct parent and child, such as siblings, grandparents, aunts or uncles.  

In a kinship care context, this typically means testing whether children are biologically related as full or half siblings, or whether another relative, such as a grandparent, aunt or uncle is biologically related to a child being considered for placement.

This differs from straightforward parentage testing, which compares a child’s DNA directly with that of a potential biological parent to give a definitive result. Because siblings, grandparents, aunts and uncles share DNA less directly, and to varying degrees, complex relationship testing requires a different type of analysis – calculating a likelihood ratio for relatedness, based on how much DNA relatives are expected to share, and how probable it is that they are biologically related.

• Sibling DNA testing determines whether two individuals are full or half siblings. Full siblings share both biological parents, while half siblings share only one.
• Grandparent DNA testing is used to establish a biological link between a grandparent and grandchild and is often used where a biological parent is not available to perform a paternity or maternity test. The test is more likely to be conclusive if both grandparents from the relevant paternal or maternal side are tested, but it can also be performed using a sample from just one grandparent.
• Avuncular (aunt and uncle) DNA testing examines the biological relationship between an aunt or uncle and a niece or nephew. For the highest chance of a conclusive result, the aunt or uncle must be a full biological sibling of the child’s possible mother or father.

In each case, the laboratory calculates a likelihood ratio to determine how probable it is that the relationship being tested exists:

• A score of 10 or above is supportive, meaning there is strong evidence that the relationship does exist
• A score of 0 to 0.1 is not supportive, meaning the individuals are unlikely to be related in the way tested
• A score between 0.1 and 10 is considered inconclusive, meaning it is not possible to determine whether a biological relationship exists based on the DNA evidence obtained

Learn more: Complex DNA relationship testing for court

What legally admissible testing requires

Not all DNA tests are suitable for use in kinship care proceedings. Where results are needed to support a Viability Assessment, Special Guardianship Order, or Child Arrangements Order, the test must be legally admissible, meaning it can be relied upon and accepted as evidence in court.

To meet this standard, testing must satisfy several key requirements:

• Chain of custody: Samples must be collected, labelled, and handled by a trained, independent sample collector, with full documentation at every stage. This ensures that samples cannot be tampered with and that the identity of each person tested can be verified.
• UKAS 17025 accreditation: This is the internationally recognised standard for laboratory testing competence, confirming that a laboratory’s processes, equipment, and reporting meet rigorous, independently assessed quality standards.
• Ministry of Justice approval: For DNA testing to be used in family court proceedings in England and Wales, the laboratory must be an approved provider on the Ministry of Justice list of accredited bodies.

This applies equally whether the test is being used to confirm a sibling relationship for kinship care or a wider family connection with an aunt, uncle, or grandparent.

AlphaBiolabs holds UKAS 17025-accreditation for DNA testing and is a Ministry of Justice-approved laboratory, providing court-admissible DNA testing that social workers, local authorities, and family law professionals can rely on.

All samples for legally-instructed tests are collected under chain of custody conditions, maintaining sample integrity from start to finish.

AlphaBiolabs’ kinship DNA testing services

AlphaBiolabs offers a full range of legally admissible complex relationship DNA tests to support kinship care cases, including sibling, aunt, uncle, and grandparent DNA testing.

Whether the goal is confirming a sibling relationship to support a joint placement or establishing a wider family connection to progress a Viability Assessment, our testing gives social workers, local authorities, and family law professionals the evidence they need to move forward with confidence.

Our legal DNA testing service offers:

• UK-wide sample collection under chain of custody, from any location within 24-48 hours of instruction, including homes, hostels, placement and foster homes, workplaces, prisons, local authority offices, and our nationwide walk-in centres. Sample collection is FREE for legally-instructed tests at our walk-in centres
• Rapid results, helping to reduce delays and meet urgent legal deadlines
• User-friendly, court-ready reports, accepted by family courts across the UK
• Dedicated Case Manager, providing expert advice and support throughout the testing process
• UKAS 17025-accredited, Ministry of Justice-approved testing performed at our UK laboratory

Kinship care cases are often time-sensitive and emotionally significant for the families involved.  

By removing biological doubt early in the process, DNA testing can help ensure that siblings, and the wider family networks around them, are given every opportunity to stay together.

If you’re a social worker, local authority, or family law professional seeking legally admissible DNA testing to support a kinship care case, contact our New Enquiry team on 0333 600 1300, email testing@alphabiolabs.com, or complete our online quote form.