Blended Families and the Life Interest Trust: Protecting Your Partner and Your Children

The most dangerous will in any blended family is the friendly-sounding one that leaves everything to the surviving spouse "in the confidence that they will look after the children when the time comes". It is friendly. It is not safe. On the survivor's death, their will decides where everything goes, and that will can be rewritten at any time, including after a new relationship, a fresh set of stepchildren, a change of heart or a period of undue influence you will not be there to see. The children of the first-to-die can find themselves inheriting nothing at all. This is not a hypothetical risk. It is a well-worn path, and it is exactly what a properly drafted life interest trust is designed to prevent.

What a Life Interest Trust Is

A life interest trust in a will gives one person, usually the surviving spouse or partner, the right to income from a fund or the right to use an asset for the rest of their life. The underlying capital is held on trust for different beneficiaries, usually the children of the first-to-die, and passes to them on the survivor's death. The survivor is the "life tenant". The children are the "remaindermen".

When a life interest arises immediately on death of the first spouse (rather than after some other event), it is technically an "immediate post-death interest", or IPDI. That matters for tax reasons that a private client solicitor will care about more than you will: an IPDI in favour of a surviving spouse qualifies for the inter-spouse exemption on the first death, so there is usually no Inheritance Tax to pay at that stage, exactly as there wouldn't be with an outright gift to the spouse. The children's rights kick in on the second death.

What It Actually Looks Like for the Family Home

The most common structure for blended families is a life interest over the deceased's share of the family home. Before death, the property is transferred into joint names as tenants in common (if it isn't already), often in equal shares, sometimes in unequal shares to reflect contributions. The will then leaves the deceased's share on life interest to the surviving spouse.

In practical terms, the survivor lives in the property for the rest of their life, exactly as they would have done with an outright gift. Depending on how the trust is drafted, the survivor can also downsize to a smaller property or move to a different location, with the trustees selling the original share, buying the new one, and continuing to hold the deceased's share within the trust. Some versions allow the survivor to release capital from the deceased's share for care costs or major expenses, with trustee consent. Others hold the line and preserve the capital strictly for the remaindermen.

On the survivor's death, the deceased's share passes to the named children. The survivor cannot rewrite that outcome by making a new will, because the deceased's share never belonged to them in the first place. It belonged to the trust.

The Alternatives, and Why They Are Weaker

Outright gift to the spouse. Simple, tax-efficient on the first death, and dependent entirely on the survivor's later behaviour and their next will. If the survivor remarries and dies without making a new will, the intestacy rules apply to their estate, and depending on the value and the new relationship, the deceased's children can end up with nothing.

Mutual wills. A separate contract between the spouses that the survivor will not change the agreed dispositions. Technically binding, but inflexible: the survivor cannot adapt to changed circumstances even where change would be sensible, and disputes about what was and wasn't caught by the mutual wills contract are common and expensive. Modern private client drafting rarely uses mutual wills for blended families. A life interest trust does the same job with more structure and fewer moving parts.

Discretionary trust for the whole family. More flexible than a life interest, because the trustees choose who gets what and when across a class of beneficiaries. Useful in specific circumstances (larger estates, business assets, or where flexibility matters more than certainty), but harder for the survivor to plan around because their entitlement is discretionary rather than fixed. For a straightforward blended-family scenario, a life interest usually gives the survivor better security.

Choosing Trustees Matters

The trustees of a life interest trust decide when consent is needed for a move or release of capital, and they hold the balance between the survivor and the remaindermen. Picking them badly is a common own goal. Two traps to avoid: making the surviving spouse the sole trustee (they should not be judge and jury in their own trust), and making children from the first marriage the only trustees (which sets them against the survivor from day one). The workable answer is usually the surviving spouse plus one or two independent trustees, or a professional trustee where the estate warrants it. We advise on trustee selection as part of every life interest will we draft.

Care Fees and the Life Interest Trust

A life interest trust is not primarily a care-fee planning tool, and the Local Authority is entitled to look at the survivor's own share of the property. The deceased's share, held in trust, is not usually treated as belonging to the survivor for means-testing purposes. That does not mean the trust is a mechanism for hiding assets: aggressive care-fee planning is closely scrutinised and easy to get wrong. The point of the life interest is family protection first, and the interaction with care fees is a side effect that varies with local authority approach.

When to Set It Up

Life interest trusts belong in the will, so they take effect on death rather than during lifetime. The moment to put one in place is when the family becomes blended (a second marriage, a serious cohabiting relationship where children from previous relationships are involved), or when a home is bought jointly and one or both parties have children from before. It is also the sort of clause worth adding when redoing a will after a bereavement, particularly if the survivor is contemplating a new relationship.

Bonsai Law drafts life interest trusts and blended-family wills as a routine part of our private client work. If your current will leaves everything to your spouse outright and you have children from a previous relationship, that's the review to book.