On the right is Prince William II of Orange, ruler of the Netherlands in the mid-seventeenth century. To his left is Mary Stuart, daughter of Charles I of England and William’s wife (if that sounds complicated, wait until I get round to William’s son, William, who married Mary’s niece, Mary).
This picture shows the pair looking fantastic, Mary shimmering in a gorgeous dress and William showing off in his tight black catsuit. Those cherubs are probably squabbling over who gets to try it on with them. If they aren’t blood relatives, they need not bother.