You are comparing two unequal situations and only lift out one part and that is not fair to either one of the two heiresses.
That means the Princess of Orange will need to acquire her own home unlike the Duchess of Brabant who will receive not only a donation but also a home. Even if her children would not all get a dotation (in Belgium very few oppose Princess Astrid receiving one btw) they will be provided with homes meaning she needs less money to provide for them.
It's like comparing the President of the USA to the President of Germany. Both are president and as such elected heads of states in a democracy but their roles are very different.
Just like the Dutch situation has been for decades, none of the siblings to these heiresses will get a state income. The financial abuse by Prince Laurent of Belgium is the scary example of how things have gome horribly wrong under a precious ruler .
BTW Catharina-Amalia's state income will be doubled the very day she marries, with consent by both the King & Parliament, so that will provide for enough 'bread & butter' methinks
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