I just came across this lovely photo of HRH Crown Prince Moulay El Hassan of Morocco (b 2003).
One of the many shortcomings of republics is that children have no formal constitutional position. Republics are so boring and stupid that only (alleged) grown-ups have even the theoretical possibility of becoming head of state or any other office, excluding a sizable proportion of the population from any possible official representation. This is blatant ageist Discrimination and must be eliminated...by the restoration of more hereditary monarchies, of course.
Of course, longer modern life expectancies make minor monarchs increasingly unlikely; Europe hasn't had one since nine-year-old Simeon II of Bulgaria was deposed in 1946. Since 1995 (when Crown Princess Victoria of Sweden turned 18), probably for the first time in history, all European royal HEIRS have been adults. But this will change on April 30 when Willem-Alexander becomes King of the Netherlands and his daughter Catharina-Amalia (b 2003) becomes heir to the Dutch throne. Certainly royal children, like all children, are happier with both parents living, so the accession of a minor is almost always tinged with sadness, but young heirs can be an inspiring and appealing symbol of the future.