Alongside Houses Organa and Teral, the Alderaan Peace Summit saw the attendance of Houses Alde, Baliss, Cortess, Ulgo, Thul, and Rist.
The planet of Alderaan was home to numerous noble families known as the Great Houses of Alderaan. Prior to the Alderaan Civil War that followed the Treaty of Coruscant, these Great Houses collectively constituted the Alderaanian Parliament, numbering forty-seven in total. However, the war's conclusion left only twenty-two Houses remaining.
House Alde was among the most ancient of the Houses, tracing its origins to the original Human settlers of Alderaan. The family took immense pride in its pure lineage, sometimes perceived as an excessive preoccupation with historical matters. Darrus Alde, a prominent figure from the House's early history, successfully brokered peace among the warring Houses at the location later named King's Pass. This unification led to the formation of the Alderaanian Parliament, with Darrus Alde becoming the first king of the planet. The estate of House Alde was situated in the Juran Mountains, in proximity to Fort Alde and the King's Road leading to King's Pass. During the Alderaan Civil War, House Alde, under the leadership of Count Alde, closely allied with House Organa and maintained strong ties with the Republic, even co-funding the Republic's Death Mark laser project.
The House of Antilles, initially known as House Antilles, stood as one of the Great Houses that weathered the Alderaan Civil War and persisted through the time of the Galactic Civil War.
House Baliss, a lesser House and vassal of House Thul, primarily survived by ingratiating itself with the more powerful Houses. Following the death of Queen Silara Panteer, the House adopted a neutral stance to align with the eventual victor. However, after Killiks overran their estate, House Baliss was compelled to seek refuge with House Teraan. Subsequently, House Baliss seized control of the Teraan estate, displacing House Teraan and establishing it as their new seat.
By the time of the Alderaan Civil War, House Qel-Nosh was an established House, a period during which the few remaining Killiks on Alderaan began emerging from hibernation. The insectoid swarms overwhelmed numerous Houses, with both Qel-Nosh and Antilles suffering military losses to these creatures.
House Serrus was among the Houses that endured at least partially through the Alderaan Civil War. Denri Ayl, during his efforts to negotiate a peaceful resolution to the conflict, paid visits to Serrus and several other Houses.
House Syrush, a minor House, maintained its estate in the southern regions of King's Pass. During the civil war, a Killik hive invaded the Syrush estate, transforming many into Joiners and partially burying the estate under debris as they excavated a cave system into the cliff behind it. Republic forces eventually liberated several members of the House and its staff who had been taken prisoner by the Killiks.