Treacherous Fires of Civil Unrest - Galaxy on Fire, #1

The Galactic Kingdom was located in the Scutum-Centaurus Arm of the Milky Way. Roughly ten thousand to fifteen thousand Light Years from SOL. It was a Kingdom of over one thousand star systems. For generations, the King and Queen would send their only child (male) to some far-off star system to grow, theoretically safe from assassins in the Kingdom. Typically, the Prince would go to one-star system, and his betrothed would be sent to another to be raised - for safety.
This practice has been done for generations. There was always someone who would want the new heir and future queen dead. Usually, the King and Queen would have one male child to ensure no rivals to the throne. By sheer accident, King Randolph and Queen Suzanne had four boys in one birth. Randolph came out first, then Francis, Rothchild, and finally Reginald. Eventually, the three brothers decide they want the throne and are willing to usurp the King and Queen and kill the rightful heir and future bride.
Lady Michelle is in Caspra (what we on Earth call the Ursae-Majoris star system), about forty-nine light years from SOL. Prince Lee was on Earth but lost to his protectors. The three brothers overthrow the King and kill him. They send fleets to wipe out all life in SOL to ensure they get the Prince. A star destroyer is sent to Caspra to kill Lady Michelle or wipe the planet out. Lady Michelle and her protection force head to SOL to find the Prince.
A small for flees the Kingdom in search of Lady Michelle and Prince Lee - still loyal to the crown. Queen Suzanne and a respectable force escape and head to SOL. Note: The Queen didn't flee by choice. The King intervened and had her whisked to a force to go to Prince Lee's aid. The three brothers send fleets at staggered times to wipe out SOL. Ingenuity on the defender's part saves SOL and Prince Lee.
The defeat of the three fleets puts the Galaxy on Fire. SOL must find allies and level the playing field with the Galactic Kingdom, which has now been broken into three Kingdoms - book two takes off from here.