How could this happen?

                                    

                                          
Astapor
Davion Baratheon woke up sweating from his nightmare and he saw Daenerys Targaryen looking at him.
"Forgive me, Your Grace," he apologized. "My nightmares don't seem to stop."
"You can tell me if you wish," Daenerys urged.
"I don't wish to burden you, Your Grace," Davion said. "Is there something that you need from me?"
"I just wish to inform you that we're leaving astapor."
"Ah, thank you, Your Grace, He said. "I'll have everything that I need and put it on the ship."
Daenerys got up to leave his room and stopped at the door, "I'm sorry for what has happened to you, my lord."
"Your sympathy means a great deal," He said. "And you may call me Davion, Your Grace."
"If I can call you Davion, then you can call me Daenerys." She said.
"Yes, Your Gra- I mean, Daenerys." She smiled at him and left his room. Davion got out of his bed and looked in his mirror, he was heir to the Iron Throne, how did his life come to this, he was the son of Robert Baratheon, he was meant to rule the kingdom, but all that was thwarted by his brother, who sold him to slavery and his mother who helped him.
Kings Landing - Two  years ago
Davion was in his bed asleep and his mother woke him up.
"Mother?"
"Your father is hurt, injured, I fear he will die." She said faking.
"I will go to him," Davion got out of his bed and got dressed. 
Royal Chambers
"Father?" Davion called out and Joffery looked at him with pure hatred.
"My boy," Robert coughed out. "Leave us"
Once the room was cleared Davion looked at his father. "You fool, how could you go hunting while drinking."
Robert laughed even though it hurt. "Only my eldest boy would talk to me in this way." He coughed. "I'm sorry Davion, I wasn't there when you needed me most. I failed you."
"No, you cannot say this now, yoy have to live, tell me this after you are healed." Davion said knowing his father will die. "I still need you, father."
"You never needed me, but I needed you, you are my heir, and I love you, more than your mother, more than Joffery and Myrcella and more than Tommen. I only wish that Lyanna was your mother. I'm sorry, my son."
"I forgive you father, for all of it, but I still need you." Davion teared up.
"Go on, son, lead them all, as Baratheon and Lannister." Robert coughed again. "Davion Baratheon, my pride."
Davion left the room in sadness, the seventeen year old boy was hurt, broken, he never agrees with the King his father was, but he knew that Robert did love him
A day later his father died and that night Davion felt his hands and legs being gripped.
"Stop! What is the meaning of this!?" He demanded.
"I'm sorry, my son, this has to happen. You will be sold as a slave, you will live out your days in exile never to return," Queen Cersei said.
"No, I've don't nothing wrong, why are you doing this!?" Davion asked.
"You're a threat," Joffery said. "And as king I have to eliminate every threat." Davions younger brother had a sinister smirk on his face.
"Mother, mother!" Cersei looked at him. "Don't do this, I am am your son."
"I'm sorry, Davion." She said with tears in her eyes and the men took him away.
Davion remembered that day as if it happened right now, how he was sold into slavery, forced to fight to survive, every night he would dream of all the people that he killed in the fighting pits for the masters entertainment, 
Daenerys had freed him along with the unsullied. She had three dragons, still small and now they were on their way to free more slaves and gain more armies to take King's Landing. Davion only had revenge on his mind, but he did miss the simpler times.
"And you ready?" Ser Barriston asked him.
"Yes," He answered. "I am now."
"I beg your forgiveness, Davion," Ser Barriston apologized. "I should've fought harder to protect you, I should've done something to help you."
"I don't blame you, Ser Barriston, my own mother and brother did this to me,: He said. "I don't want a throne, I just want them to suffer." He walked past the former Lord commander of the Kingsguard and got on to the ship.
Kings Landing - Cersei's chambers
Cersei was in her room, she had survived the Battle of the Blackwater.
"Your Grace," Varys, the master of whispers entered her room. "I bring news from the East, Astapor to be precise."
"Davion." Cersei had Varys spy on Davion to see how he was, he told her that he was fighting in the pits and won every fight. She smiled at the thought of her son being alive and a warrior just like his father. She saw Varys' facial expression change.
"What news?" She asked.
"Daenerys Targaryen landed in Astapor, and she burnt the masters and freed the slaves and unsullied."  He said.
"And my son, what of Davion?" She asked.
Varys sighed. "I'm terribly sorry, Your Grace, Davion died trying by dragon fire trying to save his master."
For the last two years everyone in te capital believed that Davion left King's Landing of his own accord, Cersei told the council that her eldest son did not want to the throne and left. Everyone saw him as a coward and Joffery loved that.
"Leave me." She said and Varys left the Queens chambers. When she was alone she broke down and cried. She hated herself for letting her son be taken. She could only pray that the gods would forgive her for this foolish act.
Hi guys so I decided to write another story.
This is just my mind going wild.
Make sure to comment and vote and tell me what you think of Davion. 
Thanks