|Photo: Dutch Photo Press|
Other attendants included the Grand Duke's sister Princess Margaretha and her husband Prince Nikolaus of Liechtenstein who came alongside their nephew Hereditary Prince Alois and his wife Hereditary Princess Sophie.
While the Grand Duchess rocked her privilège du blanc, both Grand Duke Henri and Prince Félix wore regular business suits. Princess Margaretha wore black as all other women in attendance, save for her aunt Queen Paola of the Belgians, and her husband wore tailcoat, most probably as he is Liechtenstein's non-resident ambassador to the Holy See.
Wort has a gallery of visuals dedicated to the members of the Grand Ducal Family alone. More pictures can be found at Belga, APA, Tageblatt, RTL, Dutch Photo Press and basically all over the internet.
You can see Grand Duchess Maria Teresa greeting the Prince and Princess of Monaco in this AP Video (starting at 0:16), the whole event can be rewatched on the Youtube channel of the Vatican (you can see the members of the family at around 28:23, for example).