Accompanied by their parents Prince Felipe and Princess Letizia, Princess Leonor and Princess Sofia arrived at the Madrid hospital where the monarch is recovering from a hip operation.
The adorable duo held drawings for their grandfather and smiled for the cameras before stepping inside the building.
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Following in the footsteps of their stylish parents, the blonde heiresses proved themselves to be a fashionable sister act.
Leonor wore dark blue jeans, black pumps and a stripey long-sleeved t-shirt while her younger sister Sofia, six, wore lighter denim jeans, ballet pumps, a white t-shirt and khaki jacket.
They emerged around an hour and a half later with their grandmother Queen Sofia. Leonor, who turns eight next month, held her grandma's hand tightly as they posed for the photographs and smiled and waved at the gathered crowds.
To the delight of the well-wishers, she confirmed that her grandfather is doing well.
It is the second time that the King and Queen's youngest child Felipe has been to visit his father with his wife Letizia.
The couple were also seen with Queen Sofia at the Quiron Madrid Hospital on the outskirts of the Spanish capital last week.
U.S. surgeon Robert Trousdale of the Mayo Clinic in Minnesota flew to Spain especially to carry out the three-hour long hip surgery, alongside Dr. Miguel Cabanela.
The King will have to undergo a second operation within the next two months to implant a new, permanent artificial left hip, as the one inserted last week was a temporary measure following infection in the tissue surrounding the artificial hip.
The Spanish royal family are fresh from their annual break in Majorca. Three generations of royals were spotted enjoying each other's company on the Mediterranean island at the beginning of August.
Leonor and Sofia spent time with their older cousins, Infanta Elena's children Felipe and Victoria and Infanta Cristina's four children Juan, Pablo, Miguel and Irene.