Meghan’s brother will probably toast the momentous news with a pint of Worker’s Ale in the Cedar Tree Saloon, his rowdy local bar in Oregon.
Her father, an altogether less gregarious character, will doubtless reflect on it quietly at his beach-house on Mexico’s windswept Pacific Coast. For a maternal uncle, who runs his own church in Florida, it will be a time for joyful prayer.
The unusual, out-of-the-way places where Meghan Markle’s engagement to Prince Harry was being celebrated yesterday are a stark reminder of her unconventional background, which I uncovered during many weeks spent researching her family history.
Much has also been made of her heritage, as the mixed-race descendant of plantation working slaves, a subject about which she has spoken movingly and insightfully, describing how she learned to cherish her roots — and overcome prejudice — with careful nurturing from her parents.
Her Caucasian father, Thomas, and African-American mother, Doria, bought her a set of Barbie dolls with a black mother and white father, and she was advised never to tick boxes on school forms requesting her to declare her ethnicity, but to leave them blank.
Many feel this bi-racial background makes Meghan uniquely qualified to become a member of the Royal Family in diverse, modern-day Britain, and that she will enhance their popular appeal, particularly among the younger generation. I wholly concur.
For her formative experiences — her mother would take her on educational trips to see first-hand how the poorest people live, to help her appreciate her relatively comfortable life — have profoundly influenced her character and made her the strong, compassionate, independent woman Harry will marry.
Yes, she can appear self-possessed, sometimes even a tad too keen on personal promotion, yet behind her beauty and pizzazz lies a genuinely caring character, and whether she is championing women’s rights in the Third World or campaigning for green issues, her convictions are deeply held.
Indeed, in her determination to fight injustice — and in her ability to mingle in both the humblest and highest circles, beguiling all she meets — Meghan is remarkably similar to Princess Diana. Those who know her believe she is destined to win similar adoration among the British people.
Moreover, it might be because she shares so many of his mother’s traits that Harry has chosen Meghan over a string of apparently more appropriate previous girlfriends.
Amid the euphoria, however, we should sound a note of caution, for Meghan’s storybook ascent from seedy Los Angeles tenement block to gilded palace has not been entirely plain sailing.
Certain chapters of her life remain uncharted waters — her two previous long-term relationships, as well as her time as an intern in Argentina — and there are any number of sharks among her relatives and former friends keen to capitalise on her good fortune.
Then there is her ex-husband, Hollywood producer Trevor Engelson. He is yet to explain why Meghan abruptly ended their marriage, in 2011, but will surely draw on personal experience for his forthcoming comedy TV show, about an American whose wife leaves him for a prince.
These are just the ‘known unknowns’ in Meghan’s past, to borrow a phrase. With the details of at least one other long-term relationship — her two years with the Canadian celebrity chef Cory Vitiello — yet to emerge, who can say what might yet surface?
So who is the girl who has so captivated Prince Harry? On her father’s side, Meghan descends from English, Irish and Dutch settlers who sailed across the Atlantic in the 18th century to live in an America then fighting for independence from Britain.
They sought prosperity in Pennsylvania and New Hampshire with varying success. Among her white ancestors are wealthy landowners and a lowly gas station pump attendant. They also include a father and son who fought for the Unionist North in the Civil War.
I am also told her paternal great-grandfather, ‘Papa Ike’ Markle stood 7ft 2in tall, with freakish strength to match. His physique has passed down the male generations: Meghan’s father, Thomas, now 73, is 6ft 3in and is said to top 20st, thanks to a weakness for junk food.
Another interesting character is her uncle Fred, 75, an Eastern Orthodox Catholic priest who baptised Markle babies in the river, and later founded his own church in Florida. Her father’s other brother, Mick, 77, a former senior public servant, is comfortably retired on the Oregon coast.
Her maternal ancestry is no less fascinating. Her mother, Doria Ragland’s 19th-century ancestor toiled on the Georgia cotton plantations before being emancipated after Abraham Lincoln abolished slavery in 1865, whereupon he took the name Wisdom to mark his freedom.
It marked the beginning of Meghan’s forebears’ courageous struggle to rise through American society, which remained mired in racial prejudice for a further century.
They worked as household servants and in factories before, in the Thirties, her great-grandmother broke into the professional ranks to become a teacher.
Meghan’s maternal family patriarch, her dandyish grandfather, Alvin, ran antique shops, and veered between bankruptcy and wealth (he built up an enviable collection of vintage cars).
Those bewitchingly flinty eyes, petite figure and ‘caramel’ complexion (as she calls it) come from her mother. Her distinctive curving nose is very much a Markle trait. Her personality borrows from both parents.
She has described herself as a freewheeling ‘Californian hippy’, and embraces alternative culture, like her mother, a yoga teacher.
Her ferocious work ethic derives from her father, though one hopes she has not inherited the melancholic streak that has sometimes blighted life, for this solitary man (he is now hiding in a seaside town in North-West Mexico, and has not been seen publicly since Harry and Meghan began dating).
However, Meghan’s penchant for acting certainly comes from Thomas, who developed a passion for theatre production at school and kept his colour-blindness secret to become an award-winning cinematographer.
He was in his mid-30s, and divorced with two teenage children — Meghan’s half-brother, Tom Junior, and half-sister, Samantha — when he met Doria. She was 12 years younger and temping in the Hollywood studio where he worked. They married in 1979, and two years later — on August 4, 1981 — Meghan was born.
She has portrayed her childhood as idyllic — and doubtless, through the prism of time, that is how it appears. Certainly, she was doted upon by her parents.
‘When Meggie was born, Dad was a completely changed man,’ Tom Junior told me. ‘Before then, his work took priority over everything. I remember when she came home from hospital, he had decorated the bathroom with little angels and fairies. He would keep holding her up to the mirror so she could see herself in his arms.
‘The look on his face was priceless. Meghan was a little princess long before she met Harry.’
However, there was an unpleasant undercurrent to her home life, which Meghan never mentions. According to Thomas Junior, his sister Samantha, who was 16 when Meghan was born, also wanted to be an actress, and was jealous of her — particularly when their father started taking Meghan with him to the studios and showing her off to his showbiz friends.
Samantha, 52, who suffers from multiple sclerosis and uses a wheelchair, now denies any resentment, though when news of the royal romance first broke she reportedly made cruel remarks, saying Meghan had neglected her family since becoming famous.
When Meghan was five, her parents divorced. She lived with her mother during the week, and her father — who rented a plethora of rundown Hollywood apartments — at weekends.
However, no expense was spared to pay for her education, first at the Little Red Schoolhouse, whose past pupils include Elizabeth Taylor, then the expensive Immaculate Heart Roman Catholic girls’ school. Her father’s reported $500,000 (£375,000) lottery win must have considerably eased the burden of fees.
Despite her emerging beauty, I came across only one, fleeting boyfriend from her schooldays. Meghan was rather a tomboy, according to Sonia Ardakani, the mother of her best school friend, Susie, who recalls how the girls would do good deeds such as serving at a soup kitchen for the homeless.
Meghan seemed ‘born’ for the role that now awaits her, said Mrs Ardakani. For Meghan’s compassion shone through, she says, and never more so than when Sonia’s husband was shot by a crazed gunman who walked into the garage he ran. Meghan was the first to visit him, praying for hours beside his hospital bed.
Yet she had sharp elbows, she says. ‘The thing I really admired about her is that she would fight, tooth and nail for the things she wanted in life . . . and Meghan always got what she wanted.
Perhaps so, but they didn’t come quickly. She attended university in Illinois (where her closest friend was a gay student named Larnelle Foster, who told me his unsuspecting mother harboured hopes they might marry), studying theatre with international relations, and doing an internship at the American embassy in Buenos Aires in her gap year.
Intent on a screen career, she returned to LA, but the only work on offer was demeaning, so she played upon her looks and figure. In one forgettable film, her character didn’t have a name. In the credits, she was simply ‘Hot Girl’.
She was also required to parade the stage in a crimson mini-dress, sheer tights and five-inch heels, as a ‘suitcase girl’ on the TV quiz show Deal Or No Deal.
We might have thought her romance with Engelson, a go-getting New Yorker fast making his mark in Hollywood (with whom she began living, in 2005, in a tiny, bungalow, off Sunset Boulevard) might have helped her climb the greasy pole. Alas not.
Her mixed ethnicity seemed to deter casting directors, who either found her ‘not black enough or not white enough’, she says. She had all but abandoned her dreams of stardom when, in 2010, she successfully auditioned for the role of a sassy legal assistant in Suits.
She and Engelson had finally married, in Jamaica in 2011 (Meghan wore a yellow polka-dot bikini for the post-nuptial beach drinking games), but the part required her to relocate to Toronto, where the show is filmed.
There, Meghan was feted by a chic new set of friends, among them the daughter of a former Canadian prime minister and celebrity chef Cory Vitiello, who became her boyfriend.
It is not clear whether she and Engleson were still married when that romance began, but a close friend told me the general assumption was that the affair precipitated their divorce, and that her decision to leave her husband, in 2013, came ‘totally out of the blue’.
Equally mysterious are the timing and reason for Meghan’s split, two years later, from Vitiello. Did she leave him because she fell for Harry?
Such details are for another day, however. Today the toast should be to a thrillingly unconventional future princess.