Liechtenstein: Prince Hans Adam II
As the oldest son of Prince Franze Josef II and Princess Gina, Prince Hans Adam II inherited the throne of Liechtenstein after his father's death in 1989. Surprisingly, Prince Hans Adam is the first Prince of Liechtenstein to have actually grown up in Liechtenstein, the royal family's website reveals, and he's the 15th ruler overall.
The Prince is married to Countess Marie Kinsky of Wchinitz and Tettau, and the couple has four children, three sons and one daughter. Their eldest, Hereditary Prince Alois, has already been named as his father's successor when he eventually steps down, or dies.
Even though Prince Hans Adam rules over a small country, he is Europe's richest royal, according to Forbes via Express, with his estimated net worth at $3.5 billion in 2011. His family does own the Liechtenstein Global Trust (LGT), which is the largest family-owned private wealth firm in Europe, so that's probably a big reason he has so much money!