Contesting a Will as a Sibling in England and Wales is based on grounds including lack of capacity, undue influence, or fraud. Inheritance Act 1975 claims are harder for siblings — they must show financial dependency on the deceased. There is no automatic right of inheritance for a sibling under English law.
Contesting a Will as a Sibling
When a parent or other family member dies and leaves their estate to one sibling whilst cutting out another — or divides things so unequally that it feels fundamentally wrong — the instinct is to challenge the will. The question is whether the law allows it, and if so, on what basis.
The honest answer is that siblings can contest a will in England and Wales — but the legal bar is higher for siblings than for spouses, children, or financial dependants. The grounds available depend on the nature of the dispute. Understanding which route applies to your situation is the critical first step.
Read our complete guide on contesting a will for lack of capacity.
Ground 1: Validity Challenges — Available to Anyone with Standing
A challenge to the validity of the will itself does not depend on your relationship to the deceased. Any person with a financial interest in the outcome — including a sibling who would benefit if the will were set aside — has standing to bring a validity challenge. The main grounds are:
Lack of testamentary capacity. The deceased lacked the mental capacity required by the test in Banks v Goodfellow (1870) at the time the will was signed. This is the most common ground in cases involving dementia, cognitive decline, heavy medication, or serious mental illness.
Undue influence. Another person — often a sibling, carer, or new partner — exerted pressure on the deceased that overborne their free will and resulted in a will that does not reflect their true intentions. Courts require evidence of overbearing conduct, not merely persuasion or strong family ties.
Lack of knowledge and approval. The deceased signed the will without properly understanding or approving its contents — for example, where a will was prepared by a solicitor with a conflict of interest, where the deceased could not read, or where the document was misrepresented to them.
Fraud or forgery. The will was fabricated, the deceased’s signature was forged, or a false statement was made to the deceased about a family member that caused them to alter their will — known as fraudulent calumny.
Improper execution. The will was not validly executed in accordance with section 9 of the Wills Act 1837 — for example, it was not witnessed correctly.
Where a validity challenge succeeds, the will is set aside. The estate is then distributed under an earlier valid will if one exists, or under the rules of intestacy if it does not. Depending on the family circumstances, this may or may not benefit the challenging sibling — and this is a critical consideration before committing to a challenge.
Ground 2: Inheritance Act Claims — Higher Bar for Siblings
Under the Inheritance (Provision for Family and Dependants) Act 1975, certain categories of person can apply to the court for reasonable financial provision from an estate that has failed to make adequate provision for them. Unlike a validity challenge, an Inheritance Act claim does not attack the will’s legality — it asks the court to redistribute the estate in the interests of fairness.
The key issue for siblings is eligibility. The categories of applicant under the Inheritance Act are: spouses and civil partners; former spouses and civil partners; cohabitants of two or more years; children of the deceased; persons treated as children of the family; and any person who was being maintained by the deceased immediately before death.
Siblings do not fall within any of these categories unless they can demonstrate that they were being financially maintained by the deceased immediately before death. This requires showing that the deceased was making a substantial contribution to the sibling’s reasonable needs — not merely that they were close, or that the deceased had promised them something, or that the will is unfair.
In practice, the situations where a sibling qualifies under the Inheritance Act are relatively limited but do arise — for example, where a sibling with a disability lived with the deceased and was wholly or partly supported by them financially; where a sibling who was unemployed or ill was receiving regular financial support; or where a sibling had given up work or incurred costs to care for the deceased and was in turn financially dependent on them.
Where financial dependency can be established, the court applies the general standard of reasonable provision — what is reasonable in all the circumstances, having regard to the size of the estate, the needs of all applicants and beneficiaries, and the nature of the deceased’s obligations to each.
Ground 3: Proprietary Estoppel — Where a Promise Was Made
Where a sibling was promised a specific asset or share of the estate — typically property or a family business — and acted to their detriment in reliance on that promise, they may have a proprietary estoppel claim. This route does not attack the validity of the will and does not require the sibling to be a financial dependant.
The three elements that must be established are: a clear assurance or representation by the deceased; reliance on that assurance by the sibling; and detriment suffered as a result of that reliance. The classic example is a sibling who worked in the family business for many years at below-market wages, having been repeatedly told they would inherit the business — and who then discovers the business has been left to another family member.
A sibling who has been promised a share of the family home, or who has carried out significant improvements to a property in the expectation of inheriting it, may also have a viable claim on these principles.
The Executor–Sibling Problem
A distinctive feature of sibling disputes is that one sibling is very often appointed executor. This creates a structural conflict of interest: the executor has legal control over the estate administration but is also a beneficiary — and frequently a party to the dispute.
An executor who is also the primary beneficiary under a contested will has strong personal incentives to administer the estate quickly, before a challenge can be mounted, and to make distributions to themselves. Other beneficiaries have the right to require the executor to account for the estate’s assets and liabilities, to apply to the court for an inventory and account, and in appropriate cases to apply to the High Court under section 50 of the Administration of Justice Act 1985 for the executor’s removal and replacement with an independent administrator.
Where there is a genuine dispute, challenging both the will and the executor’s conduct simultaneously is often necessary.
Realistic Outcomes for Sibling Claims
Validity challenges. Where the evidence of incapacity, undue influence, or fraud is strong — particularly where medical records support reduced capacity at the time of execution, or where there is documentary evidence of pressure being applied — sibling validity claims do succeed. Outcome: the will is set aside and the estate passes under an earlier will or intestacy.
Inheritance Act claims. Where financial dependency can be established, courts have awarded siblings significant provision. The amount is assessed by reference to the sibling’s needs and the size of the estate. Courts will not simply equalise the estate between siblings — they look at what is genuinely necessary to meet the applicant’s needs.
Proprietary estoppel. Outcomes are highly fact-specific and range from an award of the promised asset in full to a lesser remedy reflecting what is proportionate in all the circumstances. Courts have increasingly been willing to reduce the remedy where the promise was informal or where the claimant’s detrimental reliance was not as extensive as claimed.
Mediation. The majority of sibling disputes settle before trial — often for pragmatic reasons as much as legal ones. Family relationships, though often damaged by a dispute, can occasionally be salvaged through a negotiated settlement that litigation rarely achieves.
Frequently Asked Questions
Does English law require parents to treat their children equally in a will?
No. English law gives testators complete freedom to leave their estate to whomever they wish, including leaving one child everything and another nothing. There is no forced heirship rule as exists in many civil law countries. The Inheritance Act provides a mechanism for challenging unfair provision, but only for those within the qualifying categories — and for adult children and siblings, the bar is deliberately set higher than for spouses.
What if one sibling was the primary carer for the deceased — does that strengthen their claim?
It can, in two ways. First, it may support a proprietary estoppel claim if the deceased made promises about inheritance in connection with the care provided. Second, it is a factor that can be taken into account under the Inheritance Act when the court assesses what provision is reasonable — particularly if the carer sibling gave up employment or incurred financial losses in providing care. Care alone is not sufficient to establish financial dependency, but it is a relevant circumstance that courts consider in the round.
Can a sibling contest a will if they were not mentioned in it at all?
Yes. An omitted sibling has the same standing to bring a validity challenge as a named beneficiary — provided they would benefit financially if the will were set aside. If an earlier will or the rules of intestacy would benefit the sibling, they have standing to challenge. For an Inheritance Act claim, the sibling must additionally satisfy the financial dependency requirement regardless of whether they were mentioned in the will.
Conclusion
Sibling inheritance disputes are among the most emotionally charged and legally complex cases in contentious probate. The combination of grief, damaged family relationships, and high financial stakes creates an environment where clear legal advice at an early stage is not a luxury — it is essential.
Where the evidence supports a validity challenge, those claims can and do succeed. Where financial dependency can be demonstrated, Inheritance Act claims provide a genuine route to provision. And where a promise was made and relied upon, proprietary estoppel offers a remedy that operates independently of both.
Contest a Will Today has more than 30 years of experience advising families on inheritance disputes including sibling claims across England and Wales. If you have been excluded from a will or believe a sibling has received far more than they should, call us on 0333 800 2929 for a free initial conversation, or visit contestawilltoday.com.
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With over 30 years of experience across civil litigation and dispute resolution, DS Bal brings a deep, broad understanding of the legal process to every case. His background spans complex disputes involving individuals, families, and estates. LinkedIn
