Prince Harry and Meghan Markle have given Princess Charlotte and Prince George starring roles in the royal wedding - but there is still a question mark over who will walk the bride down the aisle.
Kensington Palace announced on Wednesday that Harry's niece and nephew would be among Ms Markle's six bridesmaids and four pageboys this weekend.
But there was no news about a replacement for Ms Markle's father, who has reportedly said he will not be at the service because he is due to have a heart operation.
Thomas Markle suffered an apparent heart attack last week and will reportedly undergo surgery in the US on Wednesday.
He told celebrity website TMZ that doctors would clear any blockage, repair damage and "put a stent where it is needed".
That news came after Mr Markle said on Monday that he would not be at the wedding, then told the site that he was determined to make his daughter's big day and "be a part of history".
The former lighting director's attendance at the ceremony at Windsor Castle has been speculated on widely following allegations that he posed for staged paparazzi photos.
The day after the Mail On Sunday reported that the pictures, which appeared in a number of British newspapers, were mocked up, Ms Markle's father dropped out of the wedding, according to TMZ, telling the site he did not want to "embarrass the royal family or his daughter".
But on Monday he missed a call from his daughter and she later told him she loved him in a text message and said she was concerned about his health.
Despite her parents divorcing when she was six, Ms Markle has remained close to her father.
Meanwhile, her mother, Doria Ragland, reportedly set off for London from the US on Wednesday.
She is expected to escort her daughter to St George's Chapel for Saturday's service before exchanging places with the bridesmaids and pageboys.
Charlotte, three, and four-year-old George are already skilled in the role, having performed the duty for the Duchess of Cambridge's sister, Pippa Matthews, last year.
The bridesmaids also include Harry's goddaughters, Zalie Warren, two, and three-year-old Florence van Cutsem, Ms Markle's goddaughters, sisters Remi and Rylan Litt, aged six and seven respectively, and four-year-old Ivy Mulroney.
The other pageboys are Harry's godson, Jasper Dyer, aged six, and seven-year-old twin brothers Brian and John Mulroney.
Harry has paid tribute to former mentor and close friend Mark Dyer by requesting his son Jasper as a pageboy, while Ms Markle has publicly recognised one of her best friends, stylist Jessica Mulroney, by choosing her twin sons to take part in the wedding.
Mr Dyer, a redhead like the prince, was a supportive big brother figure for Harry during the 1990s and early 2000s when the teenager was coming to terms with the death of his mother Diana, Princess of Wales.
Mrs Mulroney, who is married to Ben Mulroney, the son of former Canadian prime minister Brian Mulroney, was photographed arriving at Heathrow Airport with her family on Tuesday night.
Zalie Warren is the daughter of Jake Warren, son of the Queen's bloodstock and racing adviser John Warren, and his wife Zoe.
The palace has already announced that Ms Markle is not having a maid of honour because she did not want to choose just one person from her close-knit group of friends.