So I was reading through Belgian history and the life of King Leopold II when I stumbled upon something odd. He had 4 children, 3 girls and 1 boy.

In those times I would assume the boy would've become King after Leopold's death, but he died tragically at the age of 10. So naturally, the eldest daughter should've become Queen now, Queen Louise-Marie I.

But she never became Queen. Leopold II's nephew Albert became King of the Belgians. So now the reigning monarch of Belgium and the entire Belgian Royal family is descented from King Albert I. Why didn't Louise-Marie ever became Queen of Belgium?