Wow, this is a really cool, ambitious idea.
Kingdom of Riverhead, House Hawker
After the End War, former Cyrodiil was left with the rubble of civilization and a barren population; easy pickings for the mage-Queen Alussanah Hawker, a Redguard woman who fled Hammerfell after the war. Prior to the destruction, she had been a famed fighter and strategist, and this led her to choose the island which had formerly been the seat of Imperial power as her capitol. It was a brilliant strategic choice, both military and economic, with the water surrounding her city defending it from attack and the river serving as a great trade route. Riverhead, named so for obvious reasons, became the seat of a kingdom that stretched down the great river and its surrounding area, and enveloped the area around Riverhead all the way to the mountains that bordered Cyrodiil. The protrusion of land which bordered the sea to the west remained disputed.
Riverhead became a primarily Redguard kingdom, and given the elimination of any trappings of the old world's history had disappeared, the people once hostile to magic now embraced it with the help of the Queen. The arcane overtook the mundane, and magic permeated the people's lives; the military of Riverhead even relied primarily on its mages for making war. Queen Alussanah had even reinvented religion in order to revere the arcane; the people of Riverhead worship Juleion'r, a Redguard flavor of the old god Julianos mixed with a few other aspects of deities.
Farming and fishing communities sprung up on the fertile soil along the river, and farming and logging were the trades of the hills. Two large villages stood out among the rest: Shorewind was naturally on the shore in the south of the kingdom, and Hillcrest, you guessed it, called the northern hills its home. In the Nibenay Valley lies the Nibenay Academy, a college for mages founded by Queen Alussanah herself.
House Harker
Queen Margonet Harker - Queen of Riverhead, age 26. She is the youngest Queen in the history of Riverhead, thrust into the role when her mother stepped down. She is a strong woman and eager to prove herself, but due to her age and inexperience she is doubted.
Tavia Harker - Matriarch and former Queen of Riverhead, age 62. As all the Harker women do when they grow old and tire of the duties of Queen, she stepped down and now serves only as a public face and occasional adviser to the Queen. She was known for her shrewdness and cunning.
General Camaron Harker - Brother to the Queen, age 29. A fine mage and strategist, and a General in the Army of Riverhead. Loyal to the House, but he resents his family's wealth and power and wishes he could do his job without their political meddling.
Princess Dahlia Harker - Sister to the Queen, age 22. A pampered princess with little role in kingdom affairs beyond serving occasionally as a public face. Resents being born after Margonet, because she covets the station of Queen, and being only a Princess she is expected to soon marry for the purpose of forming a political bond with another kingdom.
Coyle Harker - Brother to Tavia and Kotoro, age 55. Ruler of Hillcrest and former high-ranking officer in the Army. Competitive with his brother Kotaro for the prominence of his town. He is always pushing for more attention to be paid to Hillcrest by the Queen.
Kotoro Harker - Brother to Tavia and Coyle, age 59. Ruler of Shorewind and former scholar in the Nibenay Academy. Is competitive with Coyle, but only because Coyle is provocative. He feels alienated by his family and is always blindly pushing for secession of Shorewind and the surrounding territory.