Here’s a guide to the bride-to-be’s extended family.
Mother Doria Ragland and father Thomas Markle married after meeting through work on US television but split when Meghan Markle was aged two.
Ragland, 61, a social worker and yoga instructor, has been called a “free spirit” by her daughter.
She still lives in Los Angeles, where Meghan Markle grew up.
Thomas Markle, 73, a former Emmy-award winning TV lighting director, has retired to a sleepy beach town in northern Mexico.
He will not be walking his daughter down the aisle after becoming embroiled in a scandal over staging paparazzi photos of himself and undergoing heart surgery this week.
The bride-to-be has a half-brother, Thomas Markle, and half-sister, Samantha Grant, both on her father’s side of the family.
The duo have been vocal about Meghan Markle since she announced her royal engagement last year — and not in the most flattering terms.
Thomas Markle Junior, 51, who lives in the US state of Oregon, has accused her of shunning the family, saying she is “probably embarrassed” by them.
He sent an open letter in April to Prince Harry asking him to cancel the marriage.
Grant has repeatedly criticised Meghan Markle’s fractured relations with her father’s relatives in interviews and on social media.
Neither are invited to Saturday’s ceremony at Windsor Castle, although her half-brother is in Britain and has visited Windsor this week, posing for a tabloid newspaper in front of the castle.
Meghan Markle has two half-nephews, Tyler and Thomas Dooley, who along with their mother Tracy Dooley have this week travelled to Britain — despite not receiving invitations to the wedding.
Tracy Dooley is the ex-wife of Thomas Markle Jr.
Tyler Dooley, 25, is a cannabis farmer in Oregon — where the drug is legal — and is reportedly developing a “Markle Sparkle” hybrid strain of marijuana for distribution.
Elder brother Thomas Dooley purportedly manages a fast-food restaurant.
Britain’s Daily Mail last month published photographs of a young Meghan Markle sitting with her half-nephews, reporting she was an occasional babysitter for the pair growing up.
Tracy Dooley, who has said she has not seen the bride-to-be in decades, announced the trio’s arrival in London Monday on Facebook, where she has set up a “royal wedding with the Dooley Markles” blog page.
The British media has been avidly chronicling the family’s visit while referring to them as part of a “circus” now surrounding the nuptials.
In 2004, Meghan Markle fell for go-getting film producer Trevor Engelson, who helped her get on the acting ladder as she struggled for parts.
They married in Jamaica in 2011.
But during their engagement, Markle landed her signature role in “Suits” which was being filmed in Toronto, with the distance putting a strain on their relationship.
A series of flops followed for Engelson while the once-struggling actress became a star.
Their two-year marriage collapsed in 2013 and the pair has reportedly not remained close.
Markle sent her rings back to Engelson in the post, according to a friend cited in a recent biography of the bride-to-be.
Meanwhile film industry website Deadline Hollywood announced last year that he was developing a pilot with Fox studios for a TV series about a man whose wife leaves him for a British prince.