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The young princesses were seen sporting matching navy blue coats and they accompanied Princess Letizia and Prince Felipe to the hospital in Pozuelo de Alarcon, near Madrid.
Fresh from their visit to Miami in Florida, Leitzia and Felipe showed no sign of jet lag.
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Mother-of-two Letizia sported jeans, black heeled boots and a warm khaki trench coat while her husband opted for a smart navy blue suit.
The family left the hospital with Juan Carlos' wife, Queen Sofia of Spain, who appeared to be in good spirits.
Earlier in the day Infanta Elena, Felipe's sister, visited her father at Quiron University Hospital.
The family's visit comes as Spain's king recovers from his ninth hip operation in three years.
At the beginning of October the king had a temporary hip implanted following an infection and his most recent surgery was put a new, permanent artificial hip in place.
Upon leaving the hospital in October King Juan Carlos told the waiting crowd that he was recovering "very well".