The late Princess Christina had equal inheritance from her mother, alike her sisters Beatrix, Irene and Margriet. And she had equal inheritance from her father, alike her three sisters and two half-sisters. Because of her eyesight problems Princess Christina always relied on financial advisers to manage her fortune.
In the last stage of her life she tried "to give with warm hand". Apart from other items, Princess Christina famously sold a drawing of Pieter Paulus Rubens for 7,2 million Euro (some 8,560,000 US Dollar) for which she was criticized in media ("not very royal for not offering it to a museum but to the highest bidder") but of course 7,2 million Euro in cash is easier to distribute "with warm hand" than a drawing.
(Thinking about the late Duchess of Alba selling a painting to purchase an expensive horse for her eldest son, the current Duke: "I can not take a Rembrandt under my arm and go to the supermarket, can I?")
Anyway, we can not look into the purses of the three Guillermo children, but most likely their late royal mother has left them comfortably provided for the rest of their life.