Registered number: 10816512.
Registered office: Squiggle Consult Ltd, Suite 2069, Letraset Building, Wotton Road, Ashford, Kent, TN23 6LN
Squiggle Consult Ltd. is a limited company registered in England and Wales.
If you have remarried, live with a new partner, or have step-children, your estate planning needs are different, and the standard solutions most couples use can fail you badly. The single biggest risk is one most people have never heard of: sideways disinheritance (your assets drifting "sideways" to your partner's family, leaving your own children with nothing).
This factsheet explains why it happens, why ordinary mirror Wills do not prevent it, and the practical tools that do.
A mirror Will (a pair of matching Wills in which each partner leaves everything to the other, then to the children) works reasonably well for a couple whose children are all shared. For a blended family, it contains a hidden flaw: a Will only controls your estate while you are alive to change yours, and the survivor can change theirs at any time.
When the first partner dies, everything passes to the survivor outright. They can rewrite their Will tomorrow. They can remarry, and in England and Wales, marriage automatically revokes an existing Will (cancels it entirely, unless made expressly in contemplation of that marriage), so even a well-intentioned survivor can accidentally undo the whole plan. They can spend it, give it away, or simply drift apart from your children over the years. Nothing in your Will binds them, because your Will finished its job the day your estate passed to them.
It plays out like this. John, a widower with two children from his first marriage, marries Margaret, who has children of her own. John and Margaret make mirror Wills: everything to each other, then split between all four children. John dies first. Margaret inherits everything, the house, the savings, the lot.
Years pass. Margaret's relationship with John's children fades. She rewrites her Will in favour of her own children, perfectly legally. Or she remarries, her Will is revoked, and on her death the intestacy rules (the legal order of inheritance when there is no valid Will) hand much of the estate to her new husband. Either way, John's children, whom he fully intended to provide for, receive nothing of their father's life's work. That is sideways disinheritance, and it is one of the most common and painful estate-planning failures we see.
If you die without a valid Will at all, the position can be even starker. Under the intestacy rules, step-children inherit nothing unless you have legally adopted them, no matter how long you raised them or how close you were. "Children" in intestacy law means biological and adopted children only. A step-parent who dies intestate leaves their step-children with no entitlement whatsoever. Our Intestacy: Who Inherits Without a Will factsheet sets out the full order of priority.
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The good news: these problems are well understood, and the tools to solve them are tried and tested. The key idea is to stop relying on a promise and start relying on structure.
A life interest trust (sometimes called an interest in possession trust) is written into your Will. Instead of leaving your share of the estate to your partner outright, you leave it to a trust. Your partner, the life tenant (the person entitled to benefit during their lifetime), can live in the home for the rest of their life and receive income from invested funds. But the capital (the underlying asset itself) is preserved, and when your partner dies, it passes to the people you chose, typically your own children.
Your partner is protected for life; your children's inheritance is protected too. Nobody has to trust anybody's future Will, because the destination of the capital was fixed by yours.
A discretionary trust (a trust in which trustees decide who benefits, when and how much, from a class of beneficiaries you name) offers maximum flexibility. It suits families where circumstances are uncertain, a child with an unstable marriage, a beneficiary who may need means-tested benefits, or a family dynamic that may change. You leave the trustees a letter of wishes (a non-binding guidance note) explaining how you would like them to act. See our Trust Administration factsheet for how trusts are run in practice.
This step is essential, and often missed. Most couples own their home as joint tenants: in plain English, you both own the whole thing together, and when one of you dies, the survivor automatically owns it all, regardless of anything either Will says. A life interest trust in your Will cannot catch your share of the house if joint ownership has already swept it to the survivor.
The fix is to sever the joint tenancy and become tenants in common: meaning each of you owns a distinct, identifiable share (usually half). Your share is then yours to leave by your Will, into a life interest trust, for instance, while your partner keeps their own share. Severing is a straightforward formal step, but it must actually be done; good intentions are not enough.
Pensions and many life policies pass outside your Will, under beneficiary nominations (the form telling the provider who should receive the money). Many nominations still name a former spouse, or were never completed at all. Review every pension and policy when your family changes, especially as unused pension funds come within Inheritance Tax from 6 April 2027 (see our Inheritance Tax Mitigation factsheet). Any new life cover must be arranged through an FCA-authorised financial adviser; Squiggle does not provide financial advice, but we work alongside advisers who do.
Even a careful plan can be challenged. The Inheritance (Provision for Family and Dependants) Act 1975 allows certain people, including spouses, former spouses, children, and people you were maintaining, to ask a court for "reasonable financial provision" if they feel unfairly left out. Claims must normally be brought within six months of the Grant (the court document confirming authority to administer the estate). A plan that protects your children but leaves your partner genuinely short, or the reverse, invites exactly this kind of claim. No plan can guarantee a claim will never be made, but a balanced, well-documented structure makes one far less likely to succeed.
In a blended family, your interests and your partner's genuinely differ, lovingly, but really. You want your children protected; they want theirs protected. Where interests diverge, each partner should have their planning considered separately, even if much of it ends up agreed and coordinated. That is not mistrust; it is the planning being done properly.
Imagine Priya and Tom, both in their late 50s, each with two adult children from previous marriages, owning a £450,000 home as joint tenants. They sever the joint tenancy, becoming tenants in common with half each. Each makes a Will leaving their half-share into a life interest trust: the survivor can live in the house for life (and downsize if needed), but on the survivor's death each half passes to its owner's own children. Priya dies first. Tom stays in the home for fourteen more years and even remarries, and it changes nothing for Priya's children, because her half was never Tom's to leave. On Tom's death, Priya's children receive her half, Tom's children receive his. Everyone was protected; nobody had to rely on a promise.
This is a hypothetical example for illustration only.
Relying on mirror Wills and mutual trust. The survivor can rewrite everything, and remarriage revokes their Will anyway. Trust is not a structure.
Forgetting the joint tenancy. A trust Will is undermined if the house passes automatically to the survivor by joint ownership. Severance is the step that makes the plan work.
Leaving old beneficiary nominations in place. Pension and policy money can flow to a former spouse entirely outside your Will.
Treating step-children as covered. Unless adopted, step-children inherit nothing under intestacy, and a vague Will can leave their position uncertain. Name people clearly.
Cutting one side out entirely. Plans that leave a spouse or dependant with nothing invite 1975 Act claims. Balanced structures are stronger than blunt ones.
DIY drafting. Trust Wills, severance and nominations interact. This is exactly the territory where homemade documents fail, take professional advice.
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This factsheet is general information for England and Wales, not legal, tax or financial advice. Last reviewed: June 2026.
Registered number: 10816512.
Registered office: Squiggle Consult Ltd, Suite 2069, Letraset Building, Wotton Road, Ashford, Kent, TN23 6LN
Squiggle Consult Ltd. is a limited company registered in England and Wales.
