Warning: Canon Character Death (Kenobi)
The twins ran around the corner and saw Kenobi and Vader in a duel to the death; their lightsabers crashing against each other.
Vader was clearly winning, Kenobi backing off as he desperately deflected the far larger man's red blade. They were saying something about masters, but Luke was too busy to figure out what their conversation was about. He lit his lightsaber, the hiss causing both Vader and Kenobi to look over at the boy.
That moment of inattention was something Kenobi would regret. Vader's blade came down, burning across his side, and Kenobi threw himself away from his former friend.
Luke charged forward with a shout, getting between the red blade and Kenobi's prone body. Leia took the opportunity to shoot at Vader, but he casually deflected the bolts without even looking her way.
"No!" Kenobi exclaimed, attempting to painfully rise from the floor, one hand on his side.
"And who is this?" Vader asked. "Did you take a new padawan? I can't see you raising anyone successfully, Kenobi. But he shall die quickly, as a mercy. No one should have you as a Master."
Luke stumbled as Vader's red lightsaber impacted with his blue one; Vader's strength overwhelming. His hands went numb from the impact. Luke swung again, wildly, and, with a flick of his wrist, Vader disarmed him; Luke's lightsaber tumbling across the room.
Luke fell backwards with a scream, clutching what remained of his right arm. His hand was gone.
Leia screamed and broke from her cover to get to Luke.
Vader raised his lightsaber to kill the boy, but suddenly Kenobi was between them, his lightsaber held high.
Taking the crushing blow and barely holding up, Kenobi grunted and snapped at Luke.
"I told you to get away from here! Take Leia and run!"
"No," said Vader, "No one will take Leia away from me. She is mine!"
Vader turned as he blocked the blaster fire that Leia had resumed, trying to protect Luke and Kenobi. He deflected the bolts, then with the Force he pushed her against the wall; her blaster falling from her hands as she struggled against his grasp.
"Leia!" Luke cried, stumbling to his feet and looking helplessly between Leia and Kenobi.
"Now, boy," said Vader, "I shall kill Kenobi, and then I shall kill you. Leia will stay with me, where she belongs."
"No," said Kenobi, still struggling against Vader's blade. "Luke, take Leia and run!"
Luke ran towards Leia, but Vader did not let him get far. Luke was lifted from the ground, his single remaining hand clutching at his throat.
"No," begged Kenobi, "Don't do this; by the Force don't do this. Not again!"
"You cannot tell me what to do and what not to do, old man. You are nothing now. I shall enjoy killing your Padawan in front of your eyes. Then you will die."
"No, you can't! You don't understand!" Kenobi was down on his knees now, holding back Vader's lightsaber as it neared his throat. "Please, please, Anakin," Kenobi rasped,
"That is not my name!" snarled Vader.
Kenobi coughed, a burn slowly etching across his throat from Vader's blade.
"You mustn't hurt them," Kenobi croaked desperately. "They are your children."
Vader reared back.
"Children?" he hissed, looking between Luke and Leia.
He released both of them; Leia immediately sprinting to Luke's side as he gasped upon the floor.
"Twins," Vader growled, his mask shifting to look down at Kenobi.
"You knew this. You knew all along. And you took them from me."
With that, he swung his lightsaber and cut off Kenobi's head.