Sebastien, never really did representative duties so no need for him to be there. Secondly, Felix and Claire partly run or are involved her family’s business and don’t really do royal duties so need for them to be there either. Just like in Liechtenstein the core family members stay in the country, but non-senior members live outside for work, business, privacy etc out of their own choices. Louis doesn’t really need to be in Luxembourg as he hardly does any representative work on behalf on the family.