Adam-Stewart told the publication, "He laughed and said 'Five children?"
Prince Harry also put on a new set of clothes as he arrived at the athletics ground, sporting a more casual grey blazer and a white shirt, which he wore open collared.
Harry and Meghan, who was wearing a Roland Mouret dress, were greeted on the portico of the north entrance to Aras an Uachtarain by Art O'Leary, secretary general of the Office of the President. In that interview, he said that the Queen's pooches demonstrated they "were immediately fond of her".
To help her transition into the royal limelight Meghan has undergone etiquette training, People magazine reports.
Katie Balfe, who is studying journalism, appeared emotional as she spoke to the duchess, telling her she was a personal "inspiration" as a high-profile advocate of women's rights.
Later today, the royal couple will visit the Book of Kells at Trinity College, Croke Park and the EPIC Irish Emigration Museum - where Ms Markle will learn about a number of her Irish ancestors.
Meghan, Duchess of Sussex in Givenchy in Ireland.
"You know, one step at a time", Harry said in an interview following the couple's November engagement.
Markle also slipped into a pair of custom suede nude pumps with a pointed toe and skinny stiletto heel by Paul Andrew.
No word yet if the official duties of the Duchess of Sussex will involve meeting more of her adoring four-legged subjects. The Duchess of Cambridge was called out by many for not joining the movement.