My son is buying a house with his partner. He is putting the largest amount of money into the purchase. How does he ensure this is taken into account if the relationship breaks down, if he dies first or if the property is sold in the future? His partner has two children from a previous relationship aged ten and nine.Tanya Jefferies, of This is Money, replies: You don't confirm this in your question but we have assumed your son and his partner are not currently married.Many unmarried couples buy property together and there are ways to protect both of their interests for the future.This is also important when there are two young children involved who need financially secure living arrangements.We asked a lawyer who is experienced in helping people in this situation to explain what legal steps your son and his partner should take at the same time as buying a home. House purchase: What extra legal steps should a couple take if they are putting in unequal sums of money? Our expert explainsRachel Spencer Robb, partner in family law at Clarion, replies: This is a situation that is becoming increasingly common as property prices rise and couples contribute different amounts towards the purchase of a home.Where an unmarried couple are buying a property together and one partner is contributing significantly more than the other, it is important to ensure that those contributions are properly recorded from the outset.Many people are surprised to learn that, currently, unmarried couples do not benefit from the same legal protections as married couples or civil partners.There is no such thing as a 'common law marriage' in England and Wales, regardless of how long a couple have been together. Rachel Spencer Robb: For now, couples who live together remain largely reliant on property, trust and inheritance law to protect their positionAlthough the Government has recently consulted on reforms that could strengthen rights for cohabiting couples in the future, those changes are not yet law.For now, couples who live together remain largely reliant on property, trust and inheritance law to protect their position.This means that if the relationship breaks down in the future, disputes relating to ownership of the property will generally be determined by property and trust law rather than the broader discretionary powers available to the family courts on divorce.In this scenario, the partner contributing the larger sum should consider putting a Declaration of Trust in place when the property is purchased.This document can record precisely how much each party has contributed and specify how the proceeds should be divided if the property is sold in the future.For example, it may provide that each party recovers their original contribution before any increase in value is shared, or that ownership is held in unequal shares reflecting the parties' respective investments.The manner in which the property is owned should also be carefully considered.Owning as tenants in common, rather than joint tenants, allows each person to own a defined share of the property and decide through their will who should inherit that share on their death.This structure is often preferable where contributions are unequal or where there are children from previous relationships whose interests need to be considered.Should the relationship break down, a Declaration of Trust can provide valuable certainty and significantly reduce the scope for disagreement.Without one, disputes can arise about what was intended at the time of purchase, particularly where one party has contributed substantially more than the other.Whilst the court can determine beneficial interests in a property, litigation can be lengthy, expensive and stressful, making prevention far preferable to cure.What else can they do? The couple may also wish to enter into a Cohabitation Agreement.This can set out broader arrangements regarding household expenses, mortgage payments, maintenance costs and other financial commitments during the relationship, as well as what should happen if they separate.Whilst discussing these issues at the start of a relationship can feel uncomfortable, it is often far easier and considerably less expensive than dealing with disagreements after a separation has occurred.The question of what happens if one partner dies is equally important. Unmarried couples do not currently benefit from the same inheritance protections as spouses.If either partner dies without a valid will, their partner will not automatically inherit under the intestacy rules.Given that one partner has two children from a previous relationship, careful estate planning is especially important to ensure that their wishes are reflected and that there is clarity regarding who will inherit their share of the property.It is also worth remembering that financial contributions do not end once the purchase has completed.If one partner subsequently contributes more towards mortgage repayments, renovations or significant improvements to the property, this can potentially affect their respective interests.Keeping clear records and reviewing any agreement if circumstances change can help avoid future disputes.Ultimately, the best protection is to have open conversations about finances from the outset and to put appropriate legal documentation in place before contracts are exchanged.A Declaration of Trust, a Cohabitation Agreement and properly drafted wills can provide certainty for both partners and their families, helping to safeguard individual contributions while reducing the risk of costly disputes in the future.The couple should also be aware that if the relationship were to progress to an engagement, a prenuptial agreement can also provide for, and protect, that initial contribution to the purchase of that property.