The Rat Queen III: The Prince. The Rat Queen, #3

Third in The Rat Queen series: It starts in the same place as the first, but outside the ship, as it took off prematurely. The family that missed the flight were relations to the Grand Duke Olav Volkovitch. The baby, who eventually became the Rat Queen, was also destined for a grand future as queen of Moskovi, the Russian planet. Everyone but Ivan, the pilot, thinks that Elton deliberately hijacked the ship, kidnapping the princess.
The story begins from the narrative point of view of the pilot, Ivan, who knows that Elton was not a pilot, but he is forced to keep quiet about it, as his life isn't his own. Through a series of events, involving political intrigue and threats of blackmail and murder, the tables are turned on the Grand Duke who now has to flee, with insufficient fuel to penetrate hyperspace. He chooses to flee to Old Earth in his personal ship, piloted by Ivan.
Also on board, is Boris, the Duke's young grandson, who has fled onto the ship to escape the deadly confrontation between his grandfather and his parents, not knowing if his parents survived. While everyone else is in stasis for the one year journey, Ivan befriends Boris, and they bond in much the same way as Elton did, with Boris's cousin, the Rat Queen. Still in orbit around Old Earth, is the space station where Strrruptl could use a human accomplice for his conquest of Old Earth.
Olav Volkovitch is just the person for the job.