As Dorothy Rowe’s classic study My Dearest Enemy, My Dangerous Friend explains, sibling relationships – invariably intense, often fraught – are among the most underexamined of familial connections. Although every sibling strives to create a unique place in the world, inescapably their longest relationships will be with loved, ignored or actively disliked brothers and sisters. 

Gifted siblings with intertwined lives present a fascinating challenge for the biographer. William and Dorothy Wordsworth’s interdependence has been dissected skilfully by Lucy Newlyn; Erika and Klaus Mann were the subject of a brilliant study by Andrea Weiss. Then there is The Knox Brothers, Penelope Fitzgerald’s strange and absorbing book about her father and his three siblings, undoubtedly a work of art which also happens to illuminate four relatively unknown figures. The historian Barbara Caine’s From Bombay to Bloomsbury, a multiple biography of the ten children of Richard and Jane Strachey, is another unexpected triumph, giving as much attention to Richard and Ralph Strachey, two older brothers who were obscure colonial functionaries, as to the younger siblings, the glittering essayist Lytton Strachey and his sister Dorothy, frustrated admirer of André Gide and author of the novel Olivia, a delicate, anonymously published study of schoolgirl lesbian passion.

Augustus and Gwen John, the subjects of Judith Mackrell’s new book, Artists, Siblings, Visionaries, have long cried out for a double biography. The Johns’ careers throw light on the instability of the art world and the vagaries of taste. Individually, they took very different paths, although neither embraced any of the particular movements of the early 20th-century avant-garde. The 2004 Tate exhibition ‘Gwen John and Augustus John’ set their art side by side, but there has been no comparable book. Shortly after Gwen’s death in 1939, Wyndham Lewis wanted to write one. That might have been a waspish, ferocious work, but nothing materialised. Both, however, have been subjects of exhaustive solo biographies; this is not a book about the undiscovered. 

A shorter book might only have attended to the moments when Augustus and Gwen were in contact. Mackrell, however, has chosen to give us much more than this, examining their lives as a whole as well. If much of the material is familiar, Mackrell is skilled at suspenseful structuring. The stories of their lives play out like a moralising Victorian tale, Augustus appearing to take the broad and easy way while Gwen, on the narrow path, finds greater artistic rewards. To defend herself from her often overbearing, oversolicitous brother, Gwen chose to live in or near Paris and guard herself against too much contact with him. She explained to Augustus, ‘We are so different! So different though our ages resemble. You have a great contempt for weakness. However there are people like plants who cannot flourish in the cold. I am one (and I want to flourish!) That is one reason why I have avoided you. Disapproval & snubs petrify me.’ Gwen feared the effects of both encouragement and criticism from her ebullient younger brother, writing to her lover Auguste Rodin, ‘I believe he will do me harm – perhaps without wishing to – if I do not avoid him.’ 

If, however, Gwen and her brother pursued their own paths in art, their romantic lives shared similarities. Gwen fell in love as easily as Augustus – with many women; with Rodin, another bearded giant and womaniser (and perhaps an older version of her brother); and ultimately with God, a father who did not let her down. Indeed, both brother and sister shunned traditional relationships and boundaries. As Virginia Ironside pointed out in 2004, ‘For both Gwen and Augustus, big, romantic, all-enveloping and unrealistic love – the kind a baby has for its mother – was fine, but “cosiness” or the normal close affection between men and women was seen as dangerous.’

Artists, Siblings, Visionaries tells a compelling story of sibling artists damaged by the loss of their mother at a young age and the emotional inadequacy of their father. If the powerful need for compensatory love felt by both siblings took different forms, it appears to have endowed brother and sister alike with an unsettling charm. Both were at the Slade in the 1890s, where their brilliance, personal and artistic, was recognised. Ida Nettleship, a fellow student, wrote on the eve of her graduation, ‘these Johns you know have a hold that never ceases – and the ache is always there in place of them when absent.’ Ida married Augustus in 1901 and soon discovered what pain the Johns could cause. It was Gwen who introduced Dorothy ‘Dorelia’ McNeill to both Ida and Augustus. This mysterious and possibly rather ordinary woman was like a blank screen onto which brother and sister projected their longings. Poor Ida was forced to accept Dorelia as an intrinsic part of her marriage to Augustus. Brother and sister emerge as intermittently cruel and dangerous to know, although Gwen’s passionate demands for love – from Rodin and from a succession of women friends – arguably did less harm than Augustus’s insouciant string of affairs.

If fears of rejection and abandonment stalked both their lives, a need for individual artistic recognition and valorisation lay at the heart of their artistic careers. To be a successful artist in the early 20th century, differentiation was key. Gender inevitably played its part too, and fortune favoured Augustus from the start. Aside from producing brilliant drawings, he looked and acted the part of an artist, not least when he took to the road in gypsy caravans with Ida and Dorelia and their children. Gwen enacted the role of the artist rather differently and in ways more attuned to the present day.

Gwen’s death in Dieppe in 1939 brought to a close the siblings’ uneasy relationship. As Augustus unpacked her work and notebooks brought over from her studio in Meudon, he was, as Mackrell observes, ‘pierced with anguish and awe’ at his sister’s achievements. Even though it is now commonplace to see Gwen as the greater artist, the way in which she chose to draw and paint was in part reactive, a creative response to her brother’s particular genius and extraordinary facilità. Augustus once rode high as a marvellous draughtsman, England’s Michelangelo, but today Gwen John seems the more progressive and thoughtful artist. When Gwen had a solo show in London in 1926, William Rothenstein, a great supporter of Augustus’s early art, understood the vital importance of her relationship with her brother, writing of her work: ‘What a rich past, what a sure and sensitive present. It is as though you once fought against Augustus’s flaming and undisciplined genius.’