Between Brothers is the thirteenth episode of ThunderCats 2011.
While the Elephants and the other ThunderCats wait and prepared for Grune and the Lizard army to attack, Panthro explains to WilyKit and WilyKat that Grune lost his tooth using it as a weapon to fight "Spidera", a giant spider, to save both himself and Panthro; the moral of the story being that "any sacrifice is worth the defeat of your enemy." Meanwhile, Grune and Slithe go against Mumm-Ra's orders and begin their next attack on the Elephants' village.
In the Astral Plane Lion-O and Tygra witness a memory from their childhood where Tygra dared Lion-O to cross a log over a deep pit. Through this memory Lion-O finds out that Tygra broke the log on purpose while Lion-O was crossing; he'd previously thought it snapped on its own. After the argument that ensues, the astral plane provides Tygra with a copy of the Sword of Omens, and Tygra and Lion-O engaged in a duel caused by Tygra's bitterness over losing both the position of king and Cheetara to Lion-O.
In the village, Cheetara defends the hut from the lizard forces while Panthro fights one-on-one with Grune. The elephants finally decide to help fight off the lizards and manage to drive most of them away.
The duel in the astral plane ends with Tygra knocking Lion-O into the pit. He then remembers that he ran and got help after Lion-O fell into the pit when they were children, and swears that he will never betray Lion-O and helps him out of the pit. They realize that Mumm-Ra has manipulated them and, as Mumm-Ra reveals himself and attacks them, Lion-O realizes that the stone they've come to find has been under their feet the whole time, holding the astral plane together. They defeat Mumm-Ra with the power of the stone, but the astral plane slowly begins to deteriorate.
As Lion-O and Tygra escape the astral plane, Panthro's fight with Grune is interrupted as the gateway begins to suck them both in. Grune seizes Panthro's wrists, to try to force Panthro to help him pull loose "or we both die!" Panthro reminds Grune that "the defeat of your enemy is worth any sacrifice!" Grune - still clutching Panthro's wrists - is trapped in the astral plane as the portal closes, severing Panthro's arms just below the shoulders. The hut explodes then, with Mumm-Ra (in crow form) flying away just in time.
Later that evening, the villagers and cats hold a celebration. Lion-O talks briefly with Panthro (who misses his scars the most) and then discusses the events in the astral plane with Anet. After Lion-O tells Anet that his prediction (of Tygra betraying him before the evening bell) was apparently wrong, Anet points out that the evening bell has yet to ring.
Outside the celebration, Cheetara approaches Tygra and tells him that she feels responsible for some of the rivalry between him and his brother. She apologizes for not being clearer regarding her feelings. Tygra is sure that she has chosen Lion-O until Cheetara tells him that she had already made her choice years ago. She tells Tygra that it was the flower he gave her all those years ago that enabled her to survive her test of patience to prove herself to the clerics. The 'Day Astrid' flower was said to contain a day of life in each of its petals. Cheetara reveals that she lived off the petals of that flower during her days of waiting and then she shows Tygra the heart of the flower that she has kept with her ever since. Cheetara confesses that she would have given up during her test if it had not been for his kindness. She tells Tygra that she has never really thanked him for giving her the flower and she wraps her arms around him and they share a passionate kiss. Unbeknownst to them, Lion-O sees them and is shocked ... as soon as the evening bell rings.
- When Panthro is healing from his wounds during the celebration, Snarf acts like a nursemaid in reference to the Snarf character from the 80's.
- It should be noted that Anet predicted that Lion-O would feel betrayed and experience a betrayal by Tygra (from Lion-O's perspective), but not literally be betrayed but feel betrayal.
- The scene where Tygra pushes Lion-O into the pit is an obvious parody of the movie "300".