There’s a mini-vogue in publishing now not so much for group biographies (how very 2019!) but for histories that take two apparently contrasted dynasties or individuals and then tease out their parallels, as well as their differences. Following on from Carol Gardner’s The Divided North, which looked at the contrasting fortunes of black and white families in Portland, Maine, in the 19th century and Jonathan W. Jordan’s Ike and Winston, which examined the lives of Dwight Eisenhower and Winston Churchill during World War II and subsequently, Caroline Hallemann’s The Kennedys and the Windsors takes on the ambitious task of following the American royal family, of sorts, and the British royal establishment, and finding links and connections between the two.

Hallemann has the self-imposed difficulty that she is writing about two of the most discussed families in the world, who have been the subjects of countless earlier titles ranging from the brilliant to the perfunctory. Even the most committed Kennedy or Windsor obsessive is likely to feel that they know everything that there is to know about them.

She dives into a story straight away that manages to make the (mis)adventures of Joseph Kennedy, the family patriarch, seem relatively fresh and unusual. When Old Joe, as he was known, arrived in Britain as U.S. ambassador in March 1938, complete with his family, it seemed for a short time like the perfect union of old and new worlds.

The Kennedys were glamorous, worldly figures who had not evaded their share of scandal—Joe was erroneously rumored to have made a fortune out of bootlegging, rather than sharply anticipating the end of Prohibition—but were still the living exemplar of East Coast sophistication. King George VI and his wife Queen Elizabeth were, by contrast, a homely and slightly uncomfortable couple who remained in the shadow of George’s elder brother Edward VIII, who had so notoriously abdicated his throne at the end of 1936 to marry the divorcée Wallis Simpson.

When Joe and his wife Rose first visited Windsor Castle, he remarked, “Rose, this is a helluva long way from East Boston,” while she lay awake that night, thinking, “I must be dreaming that I, Rose Kennedy, a simple young matron from Boston, am really here at Windsor Castle, the guest of the Queen and two little princesses.”

Needless to say, Joe’s isolationist views did not go well come the outbreak of war, and he was sent packing from his ambassadorship in late 1940 after giving an ill-advised interview to the Boston Sunday Globe.

One of the strangely fascinating aspects of the lives of both the Kennedys and the Windsors is that both families appeared to be cursed. Everyone knows about the assassinations of JFK and his younger brother Robert. But of Joe’s nine children, four died before he did—two from shootings and two from plane crashes—and his eldest daughter Rose was lobotomized at a young age.

The Windsors suffered their own share of ill luck too. George VI, worn out by the effort of leading his country through war and heavy smoking, died of coronary thrombosis aged 56, and his flighty younger daughter Princess Margaret led an unsettled and erratic life after she was refused permission to marry the man she loved.

More recently, both families have continued to be in the news through events such as the death of Princess Diana and controversies involving RFK Jr. Hallemann is excellent when concentrating on precise moments of crossover between the two dynasties, including the 1961 dinner party when JFK and Jackie Kennedy were invited to Buckingham Palace to meet Elizabeth II and Prince Philip.

In 1995, JFK’s son John Jr. met Diana in secret at the Carlyle Hotel in New York.

Relations between the two dynasties were not always warm. Jacqueline Bouvier might have described a meeting with the king and queen in 1948 as “the most exciting moment of [her] life,” but by the time she became first lady, she regarded their successors more coolly.