Feb 16, 2009, 10:15 GMT
Luxembourg's Grand Duke Henri has a serious chest infection.
The 53-year-old royal has cancelled all his engagements, including an official visit to Vietnam next week, because he is seriously ill with broncho-pneumonia.
The Grand-Ducal Palace said Henri will resume his duties "as soon as possible" but refused to give any further details of his condition.
Henri's aunt, Belgium's Queen Fabiola, has been battling the same disease in a Brussels hospital for the past month.
The 80-year-old widow of King Baudouin has been visited in hospital by King Albert II, other members of the Belgian royal family and her Spanish relatives, increasing speculation she is close to death.
But palace officials insist the queen's health is improving.
A statement said: "The condition of her health has improved slightly. She is in a serious but stable condition."
The royal was moved out of intensive care last week.
Fabiola was mistakenly declared dead earlier this month by a Belgian television station's website.
The website quickly withdrew the inaccurate story, blaming a "publishing error", and apologised to the royal family.
Fabiola - who was a hospital nurse when she met the king in the late 50s - was Belgium's queen consort between 1960 and 1993.
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