Markle, 36, who will wed Harry, 33, in May, gave a hint of what the future may hold for the young couple when they met a husband and wife team who make baby products.
Markle pointed to the product range and said, "I'm sure at some point we'll need the whole [lot]."
Earlier in the day, Harry and Markle made their first stop in Belfast at the Eikon Center, where they are attending an event to mark the second year of a youth-led peace-building initiative called Amazing the Space.
The program, launched by Prince Harry in September 2017, aims to empower young people across Northern Ireland to become ambassadors for peace within their communities and promote the idea of reconciliation across Northern Ireland.
Harry and Markle watched performances from young people in the Amazing the Space program before hearing them describe their "peace pledges."
In 1998, the Good Friday agreement brought an end to 30 years of conflict, known as "the troubles," in Northern Ireland. A key issue of the troubles was the split between the unionists, who wished Northern Ireland to remain part of the U.K., and the Irish Republicans, who wanted Northern Ireland to leave the U.K. and join the Republic of Ireland.
Harry's family had a personal connection to the violence. Lord Mountbatten — mentor to Harry's father, Prince Charles, uncle to Harry's grandfather, Prince Philip, and second cousin once removed to Harry's grandmother, Queen Elizabeth — was killed in 1979 when the Irish Republican Army (IRA) placed a bomb in his fishing boat.
Residual tensions meant security was tight for the British royal and his bride-to-be. Kensington Palace only announced the visit on Friday morning as Markle and Harry touched down at Belfast airport.
Despite this, a strong crowd of hundreds of Belfast residents and lucky tourists turned up on Victoria Street outside the Crown Liquor Saloon, one of the four locations on the couple's schedule today.
Harry and Markle enjoyed a traditional Irish lunch of stew and Guinness at the pub, which dates back to Victorian times, before meeting with well-wishers braving the rain outside.
Markle, who received a large bouquet of flowers earlier in the day, stood out in a dark green skirt and long, tan coat. Markle's cream sweater by Victoria Beckham appears to be the same sweater she wore in her engagement photos with Harry released by Kensington Palace in December.
Markle and Harry's final event was a stop at Belfasts leading tourist attraction, the Titanic. They heard the story of the ship's conception, maiden voyage, launch and stories of the ship before its infamous collision with an iceberg in the North Atlantic.
They also viewed the redevelopment and regeneration of the Titanic quarter in Belfast.
Today's visit marks the couple's first official joint visit to Northern Ireland.
Kensington Palace announced Thursday that invitations have been issued for Harry and Markle's May 19 wedding at St. George's Palace at Windsor Castle. The couple has invited around 600 guests to the wedding and a lunchtime reception hosted by Queen Elizabeth.
A smaller group of 200 close family and friends have been invited to an evening reception at Frogmore House, also on the grounds of Windsor Castle, hosted by Prince Charles.