Relationships: Life on the edge? - Boodle Hatfield

Your lawyers since 1722

06 Dec 2021

Relationships: Life on the edge?

The idea of the 'couple' is deeply embedded in Judeo-Christian culture, starting with Adam and Eve and the image of the animal world entering Noah's Ark in twos, symbolising the start and subsequent survival of the human and natural world.

Scientifically at least, we are light years away from the Book of Genesis particularly now as there is no longer any mystery surrounding paternity, contraception has liberated female sexuality and raising children is not exclusively the domain of heterosexual couples.

Perhaps as a direct consequence of these scientific advances, it seems that we may be moving away from coupledom to more complex romantic arrangements. Although bigamy remains strictly illegal in this country, polygamy (the right to have more than one legal spouse) exists in many other cultures. It is a well-known and acceptable practice under Sharia law for a man to marry up to four wives, provided each wife can be treated equally (this is polygyny). There are also fundamentalist groups in the States who continue to practise polygyny in accordance with early Mormon customs, although, this has been outlawed since the nineteenth century when Republicans referred to polygamy and slavery as ‘the twin relics of barbarism’. By comparison, polyandry (the right for women to have more than two or more husbands at one time) also exists in various communities around the world (including Nepal, for example) but this is extremely rare in comparison to polygyny.

Making a great leap forward to the twenty-first century, in Brazil, two trios (the first comprising a female cashier, female administrative assistant and a male architect and the second, three women) are known to have formalised their union under Brazil’s Civil Unions law with the ceremony presided over by a notary. The three women were apparently most concerned to ensure that their planned child would have three parents. Although Brazilian legal commentators assert that these unions are in breach of their constitution and will not give rise to the same rights as a married couple, there has been no legal decision as far as I am aware confirming those views.

Although polygamy remains conceptually at least antithetical to Western culture, in the US, research suggests that around 23% of adults live in polyamorous (as opposed to polygamous relationships). The figures are apparently roughly the same in the UK. However, the statistics are difficult to stress test due to the complex nature of the interactions and the drive of the individuals involved for secrecy (out of fear of discrimination, which might lead to loss of employment, educational opportunities etc).

What is a throuple?

Despite the potential social stigma, the new word on the streets is ‘throupling’. A ‘thruple’ or ‘throuple’ describes three people (of any combination of sexual or gender identity) in a committed sexual and romantic relationship, which may or may not be exclusive to the throuple. It is something entirely different from what might otherwise be described as an ‘open relationship’ which is where a couple (either within a marriage or committed relationship) jointly decide that their relationship no longer requires sexual fidelity to the other. Without a clear mutual agreement to this effect, engaging in sexual intercourse with a person outside of the couple relationship is infidelity and, if married, technically adultery, at least if that concept survives in law beyond the introduction of no-fault divorces next year. Even if it doesn’t, adulterers are still in breach of the Seventh Commandment (in case anyone had forgotten).

It is therefore (hopefully) fair to say that, although members of most European cultures, and definitely those of the older generation, find the paid employment of nannies, au pairs, housekeepers and cleaning ladies acceptable, the idea of the involvement of a third person in a family (in any capacity other than an employee and/or ‘granny’), particularly in a romantic or sexual sense, still seems to carry with it an element of dystopian negativity (cf. Margaret Atwood’s The Handmaid’s Tale) and/or the sense that one person in the three is being pushed out or in some way the subject of abuse, or even a victim of the patriarchy (in the case of multiple wives).

However, younger generations may be more fluid in their ideas, not least as there could be many practical advantages to living in a throuple: for example, the sharing of living costs, cleaning and childcare responsibilities, all of which are strong drivers in expensive urban cultures. The idea of a throuple could be a sign of things to come as gender roles and expectations become more fluid and surrogacy becomes increasingly widespread. We may be seeing the antiquation of ‘coupledom’ or, to echo Bridget Jones, the downfall of the ‘smug marrieds’ and be entering a new era altogether.

How does the law apply?

As ever, the law lags behind. And, without changes in the law, the legal rights and obligations within a throuple or any polyamorous relationship are complex. I am going to distinguish between two different scenarios:

  • a throuple where there are no spouses or civil partners; and
  • a throuple which includes a pair who are married or in a civil partnership.

Taking first example, I shall describe this as the ‘all’s fair in love and war’ relationship. No one in the throuple will automatically or instantly have any claims and/or rights against the other/s. However, this throuple could own property together and decide clearly how the beneficial interest in the property is to be held. They could also enter into an express contract outlining the nature of their obligations to each other (however, see further below). As with all cohabitants, absent clear property rights or a valid contract, neither party has any legal obligation to the other unless and until a child is born, whereupon Sch 1, Children Act 1989 (ChA 1989) could come into play and claims could be made for the benefit of the child. In this scenario, those claims, however, could only be made by a non-biological parent against the biological parents if the applicant is named in a child arrangement order as a person with whom the child is to live (Sch 1, ChA 1989, at para 1(1)). Therefore, if the agreement is that each child is going to be raised by three parents, then it is vital for the non-natural parent to acquire a ‘lives with’ child arrangements order under s8, ChA 1989. There is also the difficulty that financial claims cannot be made against a non-biological parent (other than a step-parent where the parties were married or civil partners, per Sch 1, ChA 1989, at para 16(2), see also T v B [2010]) thus making an enforceable contract even more important. Imagine a scenario where two women and a man live in a throuple and one has a child with a third party who is not in the throuple. Although the child may be raised in the throuple, only the biological parents will automatically have financial responsibility for the child regardless of the nature of its relationship with the other members of the throuple.

Moving on to the second scenario, ie a throuple which includes a pair who are married or in a civil partnership, which I shall describe as the ‘third party’ relationship, this could put the ‘third’ person in the throuple in a difficult position because, the party who is not legally married or in a civil partnership may have no rights or strictly limited rights in the event of a breakup. Despite popular misconception, there are no rights arising by virtue of a ‘common law marriage’. In contrast, the marital/civil partnership pair would have mutual claims against each other under the Matrimonial Causes Act 1973 (MCA 1973) or the Civil Partnership Act 2004. As above, the non-married third party could acquire property rights or, if they have a child, have the right to make claims on their behalf under Sch 1, ChA 1989 against the biological parent(s) (as above).

In both scenarios, the solution which could provide clarity to all three would be to enter into an express contract that sets out each party’s obligations to the other and what the expected outcomes would be if:

  • only one party left the throuple; or
  • the throuple breaks down in its entirety (a ‘trivorce’?).

Given that there are three separate parties, however, particular caution needs to be exercised to ensure that the agreement is enforceable in light of the common law doctrine of privity of contract.

It seems that, in an ‘all’s fair in love and war’ type relationship, the parties should, if correctly drafted, then be able to rely on the terms of their contract.  At least to the extent that the agreement is not affected or superseded by any claims under Sch 1, ChA 1989. I do wonder, though, the extent to which a court would take into account any such agreement when considering a parent’s claims under Sch 1, ChA 1989.

Where there is a married couple or civil partnership within the throuple, the potential outcomes are even less clear, regardless of whether an express contract has been entered into between the three in light of the fact that, in contrast to civil jurisdictions, you cannot oust the jurisdiction of the court to determine a financial settlement on a divorce (per Hyman v Hyman [1929]). Imagine a scenario where the throuple as a whole disintegrates (the outcome might be easier if only the third party chooses to exit) and the pair decide to divorce. To what extent would the court recognise and give any weight to the throuple contract within the divorce proceedings? Could this constitute a nuptial settlement and thus be capable of variation? Or would the court consider the rights of the third party to be inalienable and potentially comparable to a mortgagee? Would the third party need to be joined to the financial remedy proceedings? Further, to what extent would any pre-nuptial agreement be varied by a subsequent throuple agreement that does not properly take into account the agreement first in time? If the third party has a child by one of the spouses/civil partners, there could also be a competing Sch 1, ChA 1989 claim.

This analysis serves once again to underline how potentially vulnerable cohabitants (whether in a couple or a throuple) remain in this jurisdiction.

Given that polygamy is permitted in other jurisdictions, should a throuple consider marriage elsewhere, in an effort to have their relationship formally recognised and thereby be able to enforce their rights against one another in the courts of England and Wales? The answer is to proceed with caution because under s11(d), MCA 1973, as to the grounds on which a marriage is void,  if a party is domiciled in England and Wales, they cannot enter into a polygamous marriage abroad as such a marriage would be considered void in this jurisdiction.


There is an interesting clause in Article 8 (the right to respect for family life) of the European Convention on Human Rights which states that it can only be interfered with by a public authority for ‘the protection of … morals’. It fails to clarify whose morals. We forget perhaps the extent to which the world of family law remains a political arena where once ‘radical’ notions (such as a woman’s right to share marital capital) can become law. It may be that we are at the beginning of a quiet social revolution where the traditional values of twosomes are being put aside for threesomes or more. If so, the law should ready itself for change, perhaps by allowing partnership agreements for more than just couples. It is the norm in the commercial arena so, provided we can put traditional Western ‘morality’ aside, the tools enabling us to accommodate changes in family life may already be at our disposal.

Cases Referenced

T v B [2010] EWHC 1444 (Fam)

Hyman v Hyman [1929] AC 601


‘The three Brazilian brides who are challenging the traditional family unit’, María Martín, El Pais (27 October 2015)

‘One-third of Americans say their ideal relationship is non-monogamous’, Jamie Ballard, YouGovAmerica (31 January 2020)

This article was first published in the Family Law Journal (Legalease) – December 2021/January 2022 #209 edition.