As far as royal families go, Belgium's is fairly new. The nation has only been an independent country since 1830, and because there was no previous Belgian royal family from which to choose a monarch, a member of a German princely family was selected as the country's first king.
King Leopold I was born Prince Leopold of Saxe-Coburg and Gotha. He was the uncle of Britain's Prince Albert (and of Queen Victoria, too). For a time, he'd also been expected to become the prince consort in Britain; his first wife was Princess Charlotte, the only child of King George IV. She died, along with the couple's only child, in 1817. In the ensuing years, he turned down the offer of the Greek throne before finally consenting to become the first King of the Belgians.
The highest-ranking order of chivalry in Belgium is named after Leopold I. It was established in 1832, shortly after Leopold became king. The order was the brainchild of Count Felix de Mérode, a Belgian minister of state (and a nobleman who had once been suggested as a possible Belgian king). Originally, Mérode wanted to call the order the "Order of the Union." Even though that name was scrapped in favor of a name that honored the nation's new king, it lives on in the order's motto: "L’Union fait la Force" (in French) or "Eendracht maakt Macht" (in Dutch). The motto loosely translates to "united we stand, divided we fall," a phrase that holds great meaning in Belgium, a country that unites two distinct population groups, the Flemings and the Walloons.
From the start, the order consisted of two divisions: a military division that honored those who had shown bravery in combat, and a civil division that honored those who had made significant contributions to the Belgian state. In the years since, a third (rarely awarded) division has been added: the maritime division, exclusively for members of the merchant navy. Today, there are five classes of the order: Grand Cordon, Grand Officer, Commander, Officer, and Knight. The Belgian king is the Grand Master of the order.
In a flipped photograph, King Baudouin wears the Order of Leopold (1984)
As with most chivalric orders, the insignia we're used to seeing on royals (sashes, stars, etc.) are reserved for members of the order's highest class. The Grand Cordon class that wears the most elaborate insignia is generally limited to a few specific groups of people: members of the Belgian royal family, foreign royals and heads of state, high-ranking government officials, and military generals. These people are entitled to wear the collar, badge, sash, and star of the order.
The sash is a distinct purple color; the badge can either be worn attached to the sash or to the collar, which is made of golden crowns, lions, and Leopold I's monogram. The badge features a white enamel Maltese Cross set atop a bed of green laurel leaves and topped with a golden crown. In the center of the cross is a two-sided disc, which features a lion on one side and Leopold I's monogram on the other. The star is eight-pointed and made of silver, with the same central disc of black enamel with a golden lion in is center.
The Order of Leopold is awarded by royal decree. Generally, new appointments to the order are announced on specific days: April 8 (the birthday of King Albert I), November 15 (the King's Feast holiday), and occasionally on July 21 (Belgium's national day). Along with requiring certain kinds of contributions to the nation, the order has one more rather peculiar prerequisite: members must be at least 42.
Prince Lorenz and Princess Astrid wearing the sash, badge, and star of the order (2004)
Royals, however, are exempt from this age rule. King Philippe received the Leopold from his uncle, King Baudouin, on his thirtieth birthday. Queen Mathilde, who will not turn 42 until next January, is also already a member of the order, as are all of the other senior Belgian royals: King Albert II, Queen Paola, Queen Fabiola, Princess Astrid, Prince Lorenz, Prince Laurent, and Princess Claire.