The younger sister of Queen Máxima of the Netherlands has died at her home in the Argentine capital, reports say.
Inés Zorreguieta was 33 and is understood to have taken her own life.
She was bridesmaid at her sister's wedding to then Dutch Crown Prince Willem-Alexander in 2002 and is godmother to their youngest daughter, 11-year-old Princess Ariane.
Queen Máxima, a native Argentinian, was "very shocked and very sad" at her sister's death, the royal house said.
She has cancelled her forthcoming engagements, including a state visit next week to Estonia, Latvia and Lithuania which King Willem-Alexander will carry out alone.
Inés and Máxima's father, Jorge Zorreguieta, died last year at the age of 89.
He had served as agriculture minister during Argentina's brutal military dictatorship - a link that caused some controversy in the Netherlands, and led to a debate in the Dutch parliament, before his daughter married the crown prince.
Queen Máxima, 47, also has two brothers, Martin and Juan, and three half siblings.
According to reports, Inés Zorreguieta had been suffering from depression. A Dutch government spokesperson told Dutch NOS TV that her death appeared to be suicide.
She is said to have worked as a civil servant in Buenos Aires.
Tributes were paid to her on an Instagram video her brother Martin posted last year of his "very beautiful and talented little sister" singing and playing the guitar.
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