Before I learned about all of the different roles, I hadn’t realised how the Black Sheep might function in the family system, where very often they are the yin to the Golden Child’s yang. The glare of attention on the Golden Child can create a space for the family’s Black Sheep to be painted into being.

Psychologists use the term Black Sheep in family therapy to mean things like ‘the sibling who has rejected the curse of the Golden Child’ or ‘steps off the path’ prescribed by that whole ‘family narrative’. Black Sheep can feel angry and impotent, with little motivation to try to succeed, saddled with the label of ‘failure’ simply for not wanting to conform.

In truly unhappy families, ‘Black Sheep’ can be used interchangeably with the term ‘Scapegoat’, which suggests something altogether more troubling. After all, its biblical roots describe a creature forced to carry the sins of others, before ultimately being sacrificed. And sometimes that scapegoat, says psychologist Annie Wright, a specialist in family trauma, is treated like ‘the person that everyone in the family thinks “needs fixing” (or the “identified patient”)’. ‘A family unable to face up to the fact that the whole system is collectively responsible for the happiness or unhappiness of the family unit,’ she explains, ‘will instead simply pick on the scapegoat.’

Enablers and Clowns hold very different functions, although both try to detect attention away from what is really wrong in a family. Enablers will try to ‘keep up appearances’ by endlessly trying to sort and fix every slight problem. Their tendency is to empty their own tanks while attempting to rescue the person struggling.

Clowns want to avoid confronting the root cause of the family’s problems. But, instead of setting themselves up as self-appointed ‘fixers’, they take on the mantle of court jester, greeting any tension with a joke. The cumulative effect is to deny other family members the opportunity to express themselves fully: to open up, have difficult conversations or resolve conflicts.

Which gets to the crux of it all. If we feel somehow forced to ‘stay in our lanes’ – performing the same role ad infinitum – we don’t give ourselves or our siblings room to develop. At the more harmless end of the scale – in average families full of their unique foibles and oddities – it might just have a kind of mild stifling effect, making the family dynamic feel superficial and stale. At the other end of the scale, in families with serious issues, being conned into performing the same unhealthy roles on a loop can fuel real unhappiness.

It is usually better (but much more difficult) to step back and allow the natural consequences to play out. If not, you risk creating an intense and often doomed sibling dynamic. In families where the parents have enabled the behaviour of one sibling, to the dismay and frustration of the other children, therapists agree the resentment lasts well into adulthood.

Catherine Carr spoke to Louise Chunn about sibling relationships, rivalry and her new book Who's the Favourite?