House Nymeros Martell of Sunspear is one of the Great Houses of Westeros and the ruling house of Dorne. 'Nymeros' indicates "of the line of Nymeria," but generally it is simply called House Martell. The Martells of old used a spear as their emblem, while Nymeria and the Rhoynar used the sun as theirs. These were combined when Nymeria wed King Mors Martell into a gold spear piercing a red sun on an orange field.
House Martell's founding is unknown, except that they were one of the ruling families of Dorne which, since the Andal Invasion had been a collection of feuding petty kingdoms even as the other regions of Westeros began to consolidate into larger realms. When the warrior queen of the Rhoynar of the eastern continent, Nymeria, came with her people to Westeros, she took one of the strongest of the Dornishmen as her husband: King Mors Martell. Combining their strength, the two managed to unite all of Dorne under their rule; House Nymeros Martell has reigned since. The union of their peoples saw the Martells abandon many of their older Andal customs in favor of those of the Rhoynar. Specifically, they began to call their rulers "princes" instead of kings, and their lands and title passed down to the eldest child regardless of gender.
As Aegon the Conqueror waged his Wars of Conquest, he eventually came to Dorne. Here his army was bled dry by guerrilla warfare in the desert, a situation in which his dragons were of little use. Deciding that conquering Dorne would be too costly, the Conqueror opted to leave the Martells as sovereign princes. House Martell kept Dorne independent from the Targaryens for two centuries, the only one of the Seven Kingdoms to manage such a feat. After repeated failed attempts at conquest (most notably under Daeron I), Dorne eventually joined the fold through marriage between the two houses. The alliance was a dual one, with the future King Daeron II marrying Princess Myriah Martell and Prince Maron Martell marrying Daenerys Targaryen. Since then, the Martells have ruled Dorne in the name of the King on the Iron Throne, while keeping the title of Prince of Dorne.
During Daeron II's reign, the Red Keep assumed a decidedly Dornish flavor due to the influence of his Martell wife. This was one reason that many nobles opted to rise against his rule. The Martells thus defended his claim against Daemon Blackfyre.
The Princeguard:
The Princeguard was founded in 1 AL, by King Elmyrs Martell, at the request of his son, Prince Pyus, Heir to Sunspear, during the 'War of Conquest', being carried out by Aegon the Conquerer.
Prince Pyus believed that eventually Dorne would be targeted by the conquest and had the special bodyguard unit formed to protect the royal family. The original name of the Princeguard was "The Prince's Guard", a formation of 6 knights who have proven themselves in combat, with one Lord Commander to oversee them. The first of the Lord Commander's was Jorbus Dayne, a general in the Dornish Army. Jorbus was the only Prince's Guard selected by King Elmyr's himself. Prince Pyus selected the other 6 Prince's Guard. The Princeguard had played an intricate part in protecting the royal family from the Targaryan conquests.
The Prince's Guard changed it's official name to The Princeguard, after the union of Princess Myriah and King Daeron II Targaryen in 162AL. Dorne is officially subjugated into the Seven Kingdoms, by this union. King Daeron II allows Dorne to keep the status of a "Principality", hence it's leaders assuming the noble title, 'Prince' or 'Princess'. The marriage brokered a peace between House Martell and House Targaryen, after over 150 years of warfare, the Targaryen's finally united the 7 Kingdom's under one ruler.
During "Robert's Rebellion (283AL)", 5 of the Princeguard were killed; one in the defence of the Red Keep, protecting Princess Elia Martell, four during the 'Battle of the Trident', protecting Prince Lewyn Martell. Prince Lewyn ordered Ser Rymun QORGYLE, and Ser Devron VAITH to protect Prince Rhaegar Targaryen.
List of notable Princeguard:
Ser Jorbus DAYNE (55BAL - 20AL), First Lord Commander of the Princeguard
Ser Lymun MANWOODY (36AL - 92AL), Successfully thwarted an assassination attempt on Prince Eros Martell, while accompanying the young prince on a royal visit to the Free City of Pentos. It is rumored the assassin was of the mysterious religious society of assassins, known as "The Faceless Men"
Ser Harlon "the Decisive" TOLAND (128AL - 207AL), slayed Ser Tytus Lannister, and Ser Albus Mallister of the Kingsguard, and then captured Prince Aemon (TARGARYEN) the Dragonknight', during a victory over the Targaryen's, during a battle which also saw the death of King Daeron I Targaryen in combat.
Ser Rylan WYL (250AL - 283AL), killed by Ser Gregor Clegane in The Red Keep, while protecting Princess Elia Martell.
Ser Rymun QORGYLE (255AL - 283AL), killed by Lord Eddard Stark during 'The Battle of the Trident".