Romantic relationships are often imagined as involving two people. However, relationships are not the only part of our lives. Many of us have friends, family members, colleagues, and wider social networks. These relationships can be healthy and important parts of our lives.

So why can the involvement of another person sometimes create tension within a romantic relationship?

One concept that may help us understand this is triangulation.

What is triangulation?

Triangulation generally refers to the involvement of a third person within a relationship or interpersonal conflict between two people.

In romantic relationships, this might involve repeatedly comparing a partner to another person, involving friends or family members in relationship conflicts, using another person’s attention to provoke jealousy, communicating through a third person rather than directly with a partner, or creating a sense of competition between a partner and someone else.

However, it is important to emphasise that the presence of a third person does not automatically mean triangulation is occurring.

Having friendships, discussing relationship problems with trusted people or maintaining wider social relationships are not inherently unhealthy. Similarly, there may be situations in which ongoing contact with an ex-partner is unavoidable or necessary, such as when people share children or other significant responsibilities. The psychological significance lies in the wider context, pattern and function of the behaviour.

The question is not simply:

“Is there a third person involved?”

It is more:

“What role is the third person playing within the relationship dynamic?”

Why might triangulation occur?

There is no single explanation for why a third person might become involved in a relationship dynamic.

Sometimes, this may reflect insecurity or a desire for reassurance. For example, someone may mention another person’s interest in them to seek reassurance that their partner cares about them.

In other situations, a third person may become involved because direct communication is difficult. Instead of expressing dissatisfaction directly to their partner, someone may complain about them to another person or use that person as a means of indirect communication.

A third person may also become involved in a way that creates competition.

For example, repeatedly drawing attention to another person’s attractiveness, interest, or availability may lead a partner to feel they are being compared to someone else.

This can create uncertainty:

“Am I enough?”

“Are they more interested in this other person?”

“Do I need to compete for their attention?”

That uncertainty can become psychologically powerful and, for most people, probably quite a painful experience.

The psychology of jealousy and comparison

Jealousy is a complex emotional experience. It can involve fears of losing a valued relationship, concerns about rejection and comparisons between oneself and another person.

When another person is repeatedly introduced into a romantic relationship, it can create a sense of competition.

A partner may begin to compare themselves with the third person:

“Are they more attractive than me?”

“Are they more interesting?”

“Does my partner prefer them?”

This is one reason triangulation can become emotionally destabilising. The issue is not necessarily the third person themselves. It is the uncertainty created around the relationship.

The relationship can begin to feel less like a secure connection between two people and more like a competition for someone’s attention, affection or commitment.

When can triangulation become harmful?

Not every interaction involving a third person is harmful, but like lots of things, the context matters. There is a significant difference between discussing a relationship problem with a trusted friend and repeatedly involving other people in relationship conflicts, which creates insecurity or competition.

There is also a difference between having unavoidable contact with an ex-partner due to shared responsibilities and repeatedly emphasising that person’s attractiveness, desirability or interest in order to provoke a reaction from a current partner.

When trying to understand whether a behaviour has become part of a harmful relational pattern, it can be useful to consider several factors. Is the behaviour an isolated event, or does it occur repeatedly? Is it openly discussed, or deliberately concealed? Is the person attempting to communicate directly with their partner, or are they involving another person instead? Does the behaviour repeatedly create feelings of insecurity or competition? Is it being used to gain power or control? What happens when the partner explains that they are being hurt? Is there accountability and a willingness to change?

These questions help us move beyond simply labelling a behaviour and instead consider the wider relational dynamic.

Triangulation and power

One reason triangulation can become harmful is that it can change the balance of power within a relationship.

If one person repeatedly creates uncertainty about their partner’s position, the other person may begin to feel that they need to compete for security.

They may become increasingly focused on monitoring their partner’s behaviour, comparing themselves with others, seeking reassurance, trying to prove their worth, or trying to prevent their partner from losing interest.

The relationship can gradually become organised around managing uncertainty.

This does not necessarily mean that everyone who creates jealousy is consciously attempting to control their partner. Human behaviour is often more complicated than that.

People may act out of insecurity, fear of abandonment, a desire for reassurance, or poor communication skills.

However, a behaviour can still have harmful effects even when the person engaging in it does not fully understand or intend those effects.

This is one reason why the psychology of relationship harm can be so complex.

The third person is not always the problem

One reason triangulation can become harmful is that it can change the balance of power within a relationship.

If one person repeatedly creates uncertainty about their partner’s position, the other person may begin to feel that they need to compete for security.

They may become increasingly focused on monitoring their partner’s behaviour, comparing themselves with others, seeking reassurance, trying to prove their worth, or trying to prevent their partner from losing interest.

The relationship can gradually become organised around managing uncertainty.

This does not necessarily mean that everyone who creates jealousy is consciously attempting to control their partner. Human behaviour is often more complicated than that.

People may act out of insecurity, fear of abandonment, a desire for reassurance, or poor communication skills.

However, a behaviour can still have harmful effects even when the person engaging in it does not fully understand or intend those effects.

This is one reason why the psychology of relationship harm can be so complex.

The third person is not always the problem

It can be tempting to focus on the third person:

“Who are they?”

“What do they want?”

“Are they a threat to the relationship?”

But sometimes, the more important question is:

“Why has this person become psychologically important within the relationship?”

The third person may not have done anything wrong. They may not even know that they have become part of a relationship dynamic.

The issue may instead lie in how one partner introduces, discusses or uses the relationship with that third person.

This is an important distinction.

The problem is not necessarily the existence of other relationships. Romantic relationships do not require people to abandon all of their friendships, family relationships or wider social lives.

However, how relationships with other people are managed can still be significant within a romantic relationship. This may be particularly relevant when another person is repeatedly used to create insecurity, competition, uncertainty or indirect communication.

Understanding patterns rather than isolated behaviours

Perhaps the most important thing to remember is that relationship behaviours should be understood within their wider context.

A single mention of another person is not necessarily triangulation.

Having a close friend is not necessarily triangulation.

Talking to someone else about a relationship problem is not necessarily triangulation.

The same behaviour can have very different meanings depending on the wider pattern in which it occurs.

This is why psychological understanding requires more than simply asking:

“Did this behaviour happen?”

We might also ask:

What function did it serve?

How often did it occur?

How did it affect the relationship?

Was there a pattern of creating insecurity or competition?

Could the people involved communicate directly and repair the resulting harm?

Triangulation is therefore not simply about the presence of a third person.

It is about the psychological role that the third person comes to play within a relationship dynamic.

Sometimes, this may reflect insecurity or poor communication.

Sometimes it may become part of a recurring pattern that causes emotional harm.

Understanding the difference requires nuance.

Because relationships are rarely defined by one isolated behaviour.

They are shaped by patterns.