Princess Marie Astrid of Luxembourg was born on 17 February 1954 as the daughter of Jean, the then Hereditary Grand Duke of Luxembourg, and Princess Joséphine-Charlotte of Belgium. She was their eldest daughter, and four more siblings, Henri (born 1955), Jean (born 1957), Margaretha (born 1957) and Guillaume (born 1963), followed.
Her godparents were Leopold III, King of the Belgians and Charlotte, Grand Duchess of Luxembourg. She received her name in honour of the Virgin Mary and her maternal grandmother, Queen Astrid. She was educated in Luxembourg and Belgium and obtained a nursing degree from the Luxembourg Nursing School in 1974. She became President of the Luxembourg Youth Red Cross in 1970. During the late 1970s, it was rumoured that she was to marry the future King Charles III of the United Kingdom. This would have been unlikely due to differences in religion.
On 6 February 1982, Marie Astrid married her second cousin Archduke Carl Christian of Austria1, who was the grandson of Austria’s last Emperor. It was a grand wedding with many royal guests in attendance. They went on to have five children together: Marie-Christine (born 1983), Imre (born 1985), Christoph (born 1988), Alexander (born 1990) and Gabriella (born 1994). She already has numerous grandchildren.
I think the story about Marie-Astrid marrying Charles was basically a rumour spread by the British tabloids. Religion would have been a factor: reportedly Catholics who marry into the British royal family must give up their religion. For example, Autumn Kelly, a Canadian woman who married (now divorced from) Princess Anne’s son, converted to Anglicanism from Catholicism. I also think Marie-Astrid, if she married Charles, would have had to compete with Camilla.