According to Royal Blog The Grand Duke will attend the funeral of his uncle Prince Alexander of Belgium. The funeral of Prince Alexander will be held tomorrow in Laeken. The Prince will be interred in a crypt in the chapel adjacent to the Royal Crypt at the Church of Our Lady.
It is not confirmed but I highly suspect that The Grand Duchess will be in attendance with Henri and that his sisters and their husband's (they are close to their Belgian relatives) will attend.
Prince Alexander, born July 18, 1942, was the child of Leopold III, King of the Belgians and his second, much vilified, wife Princess Lilian (nee Baels). He died November 29, 2009 of an acute pulmonary embolism. He was predeceased by his elder (half) siblings Baudouin, King of the Belgians and Grand Duchess Josephine-Charlotte of Luxembourg. He is survived by his wife Lea who is styled as Princess Alexander of Belgium, his older (half) brother Albert II, King of the Belgians and his two younger sisters Princesses Marie-Christine and Marie-Esmeralda of Belgium.
I've read many comments since the death of Prince Alexander about the relationship between himself and his siblings. I consider several of these comments to be in bad taste. Prince Alexander seemed to enjoy a good relationship with his elder siblings from the first marriage of their father. The same cannot always be said for his younger sister Princess Marie-Christine who had a rather difficult relationship with not only their siblings but their parents. The relationship between the children of Queen Astrid and their step mother couldn't have been as bad as the press leads us to believe considering that Grand Duchess Josephine-Charlotte named her first child after both her mother and her step-mother.
I just want to point out that I am really not comfortable with the term "half uncle" that other people seem to prefer. I'm only moderately more comfortable with the term "half brother." I have five "half uncles" and and two "half aunts." They would feel insulted and disrespected if I ever introduced them as my "half" aunt or uncle. I understand that, perhaps, this term is useful from a genealogical prospective but I have a hard time accepting that any person of decorum would use the term "half uncle" while referring to their relatives. Seriously, either your an uncle or you aren't. Does a "half" uncle somehow act as an uncle only half of the time?