Rivalries - they run in the family

The Princess Royal at 5.45am on Britain's Radio 4 Farming Today show, expressing her support for genetically modified crops. Illustration / Rod Emmerson

It wasn't an interview you'd think a lot of people got to listen to. The Princess Royal at 5.45am on Britain's Radio 4 Farming Today show, expressing her support for genetically modified crops.

One person who is unlikely to have overlooked the interview on Thursday, however, is her elder brother, the Prince of Wales, a passionate organic farmer and anti-GM stalwart. As the Princess remarked: GM is "one of those things that divides people" - specifically, one assumes in this instance, siblings.

Prince Charles and Princess Anne no doubt manage to keep their differences amicable, unlike the legions of siblings who have come to blows over Scottish independence, Brexit, Trump, and any number of incendiary issues of late.

Not that it tends to take much to push brothers and sisters over the brink. The family dynamic is inherently Darwinian, albeit a case less of survival of the fittest than survival of the complete bastard.

Those who defend this sort of conflict as being "only natural" presumably have in mind the black eagle, a species in which the mother lays two eggs, the first-hatched offspring pecking the next in line to death.

Or perhaps the blue-footed booby, where brood hierarchy means that - in times of scarcity - the eldest will physically eject its brothers and sisters from the nest.

A quarter of spotted hyena pups are killed by their siblings. (At this point, I should probably 'fess up to having seen off my own twin in the womb: he or she appeared to abort at five months, while I left the hold at seven, and can claim to have lone twin syndrome.)

Genetically speaking, one is closer to one's siblings than even one's parents, yet rarely do individuals appear more different, striving to individuate themselves as they do. I say this as the eldest of five hugely contrasting personalities, who neither look nor behave particularly alike, and with a father who refused all contact with his twin for his last quarter-century. Birth order and character traits obviously play their part, but evidence suggests that it's the adults who screw things up, making rivals out of playmates.

Despite the poet Philip Larkin, it's not only your parents who f*** you up. One Christmas, my grandmother, in her wisdom, decided to present me with a fur coat and diamond ring, but give nothing to my sisters, compounding the matter by informing them that they were "too fat" for such gifts. "You can't be too fat for a diamond," came my sister's arch response. Then again, maternally inspired savagery once led one of my siblings to send me texts wishing me dead on my birthday, so Grandma can't take all the blame.

Many of Western culture's foundational narratives rest on tales of sibling warfare, be it Cain and Abel, Jacob and Esau, or Rachel and Leah. Joseph's green-eyed brothers resented him so intensely that they sold the poor blighter into slavery. Romulus dispatched Remus after a serious town planning dispute, while bad blood doesn't begin to describe the enmity between Thyestes and Atreus, the latter tricking the former into eating his own sons for dinner.

Shakespeare often based his plots on sibling friction, be it Richard III, The Tempest, As You Like It or King Lear, while HBO's Game of Thrones follows history in putting the Lannister, Targaryen and Baratheon broods in a perpetual state of internal riot.

Indeed, it is where inherited power has been at stake that the gloves have really come off. Cleopatra kiboshed two brothers and a half-sister lest they snap at her sandalled heels. The Roman emperor Septimus Severus foolishly made his sons Caracalla and Geta joint successors in AD 198. The decision to split the empire in half - Geta claiming Asia and Egypt, Caracalla Europe and Africa - was not enough for the latter, who had his brother assassinated, Geta dying in their mother's arms.

Despite being William the Conqueror's eldest son, Robert Curthose never secured his father's crown, pipped to the post by younger brother Henry I. While the story of the jealousy between the sons of Henry II was sufficiently notorious to be fictionalised in Robin Hood, Ivanhoe and The Lion in Winter.

The hostility between half-sisters Mary and Elizabeth Tudor was not helped by their being poster girls for rival religions, or Mary's securing a husband who gave every sign of preferring her younger sister. Elizabeth's mother, Anne Boleyn, had maintained her own state of sibling strife, reaching its apotheosis when she succeeded her sister Mary as Henry VIII's lover.

Dynastic power no longer being what it was, these days sibling conflict tends to centre on career rivalry. Tennis stars Venus and Serena Williams may be able to keep their competition friendly, but other sibling combos have not been so fortunate. The 20th century's most celebrated case came in the bitter antagonism between Hollywood legends Olivia de Havilland and her younger sister Joan Fontaine, who vied for stardom as they had their mother's affections.

The two went up for the same Best Actress Oscar in 1942, Joan winning the gong, Olivia refusing to congratulate her. They ceased to communicate after their mother's death in 1975, Fontaine remarking: "I married first, won the Oscar before Olivia did, and if I die first, she'll undoubtedly be livid because I beat her to it." Fontaine did indeed die first in 2013, the pair unreconciled.

Similarly, sisters and sparring writers Margaret Drabble and A.S. Byatt are still not on speaking terms. Their aggressively ambitious mother was determined that her daughters should follow her in attending Newnham College, Cambridge, to read English: the younger, Drabble, trumping Byatt's second-class degree by being awarded a starred first. Byatt remarked that, even at the age of 10, "I always felt as though somebody were sort of breathing on my heels and whatever I did was not quite good enough."

By 1990, their rivalry was sufficiently red in tooth and claw for a rumour to circulate that Drabble had wagered $100 on her sister winning the Booker Prize, so that - should this happen - there would be something to sugar the pill. To this day, their belligerence makes the Miliband brothers look fond of each other.

Still, even the Pankhurst sisters found cause for dispute, Christabel being mother Emmeline's favourite.

My own solution in the cause of familial peace and reconciliation is to defer to my youngest sibling in all things. In the first instance, this serves as necessary table-turning after the poor chap's lifetime of being bossed about by four older siblings. In the second, having spent his entire life stage-managing our competing rivalries, his diplomatic skills know no bounds.

How to stay on friendly terms with your sibling

It's probably the longest relationship you'll ever have, and studies show it becomes increasingly important to us the longer we live. Yet while there is plenty of information to help parents manage their children's rivalry, there is almost nothing to help you if you fall out with one of your siblings in later life. Understanding the key characteristics of different sibling relationships first, is vital.

Older brother/younger sister
Usually a protective relationship, with the older brother looking out for his sister. It can, however, cause a sister to feel resentful if her brother was granted more status and privilege when young.

Older sister/younger brother
Generally a nurturing/nurtured relationship, especially true if the sister is also the eldest child, because she's likely to assume the caring role both as eldest and as a girl.

Two sisters
Although often rivalrous when young, research shows that sisters are the closest of sibling pairs as adults, especially if they have children near the same time.

Two brothers
The closer they are in age, the more likely they are to compete, particularly if parents value the accomplishments of one brother over those of the other.

Twins
This relationship tends either to be incredibly close and supportive or intensely rivalrous. The key is whether, as children, parents treated them as two of the same (rivalry), or looked for and praised the individuality of each (closeness).

●If you feel distant from your sibling, remind them of positive shared experiences during childhood, and if possible try to recapture some of them. If you've fallen out over some issue, think ahead 10 years. Will that issue still be as important as a strong relationship with your sibling? If not, try to set the issue aside and see if you can re-establish your bond. You may still have much to share and treasure together.