Meghan Markle will be the first mixed race person in modern history to marry a senior British royal.
Commentators have already described Prince Harry's relationship with Ms Markle, whose father is Caucasian and mother is African-American, as love transcending race in the most traditional institution in Britain.
Historian Kate Williams wrote in The Guardian: "In a court and household that is still about as white as it was in Victoria's day, perhaps change has to start at the top."
For an opinion piece in the Metro, video journalist Funmi Olutoye described the significance of the romance.
"Never in a million years did I think someone in the Royal Family would be romantically involved with someone whose skin is a darker hue than theirs," she said.
"It speaks volumes about how society is changing, albeit slowly. But it's definitely changing."
She added: "Love has transcended race in the most traditional institution in Britain."
Ms Markle wrote of her own background: "While my mixed heritage may have created a grey area surrounding my self-identification, keeping me with a foot on both sides of the fence, I have come to embrace that.
"To say who I am, to share where I'm from, to voice my pride in being a strong, confident mixed-race woman."
She has recounted the racism faced by her grandfather, who told her as a child how he and his family stopped off at Kentucky Fried Chicken during a road trip, but had to go to the back of the restaurant for "coloureds" and eat the chicken in the parking lot.
"That story still haunts me," she said. "It reminds me of how young our country is. How far we've come and how far we still have to come."
In a piece for ELLE Magazine in 2015, she told how she witnessed her mother being called "the N word" by another driver in LA and described the heartache it caused.
She also described how her great-great-great-grandfather went on to create his own identity when freed from slavery.
"Because in 1865 (which is so shatteringly recent), when slavery was abolished in the United States, former slaves had to choose a name. A surname, to be exact," Markle wrote.
"Perhaps the closest thing to connecting me to my ever-complex family tree, my longing to know where I come from, and the commonality that links me to my bloodline, is the choice that my great-great-great grandfather made to start anew. He chose the last name Wisdom."
Markle may not be the first mixed race woman to marry a senior British royal in the history of the monarchy.
In 1999, the Queen's first cousin once removed, the Honourable James Lascelles, son of the late 7th Earl of Harewood and great-grandson of George V, married Nigerian actress Joy Elias-Rilwan.
At the time, the law required that the monarch approve all marriages of those in direct line of succession to the throne, including that of rock musician James who is way down the list at around 57th in line.
In 2004, New Zealander Gary Lewis became the first Maori to marry into the British Royal Family when he wed the Duke of Gloucester's daughter Lady Davina Windsor, who was then 20th in line to the throne.
Prince Harry's future in-laws - and the rest of Meghan's squabbling family
Meghan Markle is close to her "free-spirited" mother and her "thoughtful, inspiring" father.
The actress has written lovingly of her relationship with both.
But it is the star's extended family which has hit the headlines, with one newspaper describing it as a "motley collection of individuals who, between them, have a long record of boozing, bust-ups and bankruptcies".
From a gun crime arrest to a Twitter rant accusing the Suits actress of hypocrisy, Markle's step-relations have already proved controversial so far.
Here's a look at Prince Harry's future in-laws.
Meghan Markle has described her mother as a "free-spirited clinical therapist".
Writing on her lifestyle blog, she told how her mother took her to visit the slums of Jamaica and to see poverty in Mexico when she was just 10.
"My mother raised me to be a global citizen, with eyes open to sometimes harsh realities," Ms Markle revealed.
Ms Ragland, who is African-American, met Meghan's father, Thomas Markle, on the set of the US soap General Hospital, where he worked as a lighting director when she was a temp in the studio.
"I like to think he was drawn to her sweet eyes and her Afro, plus their shared love of antiques," Ms Markle wrote.
They divorced when Ms Markle was six. Although she lived with her mother in Los Angeles, Ms Markle also spent a great deal of time with her father.
Ms Ragland has worked at a day centre for adults with memory loss and as a yoga therapist.
Ms Ragland, who filed for bankruptcy in 2002, has kept her daughter's counsel despite the press interest.
Thomas Markle is a former TV lighting director who worked on shows such as hit sitcom Married... with Children and popular US drama General Hospital.
He won two Emmys for his team's work on General Hospital and was nominated for countless others.
Markle is his only child from his second marriage to Doria Ragland. He has two older children from his first marriage to Roslyn Markle.
He lives a quiet life in Mexico and filed for bankruptcy in 2016 after reports he failed to pay his debts.
Markle is close to her father, who is of Dutch and Irish descent, and has described him as hardworking and caring and believing in her "grand dream" of becoming an actress.
Samantha Grant - also known as Samantha Markle - describes herself as a writer, a mental health counsellor and a "blabbermouth".
She is Ms Markle's half sister from her father's first marriage. A one-time actress and model, she was diagnosed with multiple sclerosis in 2008 and uses a wheelchair.
Based in Florida, she is 17 years older than Markle and sells jewellery to raise money to fund the feature films she writes.
Twice-divorced, she has three children - Ashleigh, Christopher and Noelle.
Like her father, she filed for bankruptcy and is estranged from her mother Roslyn - Thomas Markle's first wife - and brother Thomas Jr.
Ms Grant has been an outspoken critic of Ms Markle since news of her relationship with Harry broke, describing her in interviews as a "shallow social climber" and claiming she shunned her since making it in Hollywood.
"The royal family would be appalled by what she's done to her own family," she said.
She said Markle had barely spoken to her she was diagnosed with MS nearly a decade ago. She later maintained she never made the critical comments of her half sibling.
Ms Grant claimed she raised Ms Markle for 12 years while she was growing up in California but her ex-husband, Scott Rasmussen, disputed this.
Meghan Markle's half brother Thomas Markle Junior, 50, has been bankrupt once, divorced twice and faced trial on gun charges before the case was dropped.
The father-of-two lives in Grants Pass, Oregon, and works as a window fitter.
He was arrested in January 2017 for allegedly holding a gun to his girlfriend Darlene Blount's head during a drunken argument.
Charged with unlawful use of a dangerous weapon and menacing domestic violence, he faced jailed for up to five years if convicted. The charges were later dismissed. He apologised for his actions and said he was seeking help for his drinking problems.
Mr Markle Jr is not thought to be in contact with his famous half-sister but has given interviews about her and shared family photos with the media.
Meghan's father's first wife, Rosyln Markle is mother to Samantha Grant and Thomas Jr.
Roslyn has said of her estranged daughter: "Everything she has said about Meghan is a lie."
The 71-year-old lives in Albuquerque, New Mexico, and has been complimentary about Ms Markle.
"Meghan is very pretty, very nice, very polished and very classy. I never hear anything but good about her from my son Thomas (Jr)," she said.
She also has a younger son, Bobby Lucero.