Boys' Clothes European and American Children's fashions, especially in the 19th and early 20th centuries were strongly influenced by the way royal families dressed their children. Queen Victoria was especially influential as so many of her children and grandchildren maired into royal familes throught Europe. Kaiser Wilhelm II, for example, was the Queen's grandson. The geneology of European royalty is a huge under taking, given the large number of countries and principalities. Major changes have ocurred over time with countries created, dsmantleted, and reappearing.
Some royal lines extend more than a millenium, others only a few generations.
Royal lines can be looked up on the internet with a convenient search engine . The Hapburgs were one of the Eueopean ruling families with the longest histories. I have some informarin about the family of the last Hapsburg Emperor of Austria Hungary. The dress of the Austrian royal family appears to have influenced how wealthy families dressed boys within the Empire, but had no great influence on European styles in general or on the clothes of other social strata. The Belgium crown only dates from the 1830s.