Speaking of them, let me ask for confirmation and clarification:
Victoria has five reigning descendants today; Christian IX has six. Four of the ten European sovereigns (UK, Norway, Denmark, Spain) descend from both.
The king of Sweden descends from Victoria, but not Christian IX; he does, however, descend from a brother of Christian IX. Can anybody name that brother? I searched through sites, but was unable to trace him.
Conversely, the king of the Belgians and the grand duke of Luxembourg descend from Christian IX, but not Victoria; both, however, descend from King Leopold I of the Belgians, who was a mutual uncle of Victoria and Albert.
The king of the Netherlands is the only king in Europe who does not descend from either. He does, however, descend from King George II of Great Britain, who was a mutual great-great-grandfather of Victoria and Christian IX. Christian IX and his queen consort, born Princess Louise of Hesse-Cassel, were second cousins to each other and third cousins to Victoria.
If one is interested in the subject of religion, all but one of Victoria's five sovereign descendants are Protestants, whereas Christian IX's sovereign descendants are evenly divided between Catholics and Protestants. Unsurprisingly, the three Protestant sovereigns who descend from the latter (UK, Norway, Denmark) also descend from Victoria. The king of Spain is the only Catholic sovereign who descends from both.
Is all this correct? I'm most interested in the data on Catherine, the brother of Christian IX, and the relationship between Victoria and his wife.