Kankuro is afraid of Gaara right after he killed the rain nins, but he still reached out and grabbed Gaara by the front of the shirt, and said, "Why can't you listen to your older brother for once?", and then Temari appealed to Gaara as the older sister, and that's when Gaara said that he never thought of them as his siblings.
Now that I think about it, I don't think he was repeating himself. Furthermore, during the fight against Rock Lee, his team has noted that this exam has made him more unstable.
What I draw from that is that while Gaara has always been unstable, what with the lack of sleep, being the one-tail, having a douchebag for a father, and then the incident with Yashamaru...normally, he actually wasn't as crazy and as bloodthirsty as he was during the Chunnin exam.
I'm not rewatching everything in order, before this, I was watching Gaara and Lee's fight against Kimmi-bones, and remembering how Maldoror had pointed out within the Diplomatic Relations LeeGaara series, that having to kill Kimmi-bones with the Avalanche of Sand was a huuuuge waste of chakra, and I remember wondering why Gaara sand coffin people instead of choking them with sand, cause wouldn't the later waste less energy?
...and so, in episode 34, Gaara actually said to the big rain nin, that "I could cover your loud mouth and kill you, but that would be very miserable on your end", so he chose instead to sand coffin the rain nins, something that Gaara explains as being painless because it happens too quickly!
If Gaara had always been as outwardly crazy as he was during the Chunnin Exams, I don't think he would have been sent on such an important missions, especially when he threatens their sensei and siblings, three other very useful ninjas that a resource depleted Suna needs. We saw in the flashback how Gaara had craved to belong, mere existence wasn't enough for him...I think that even after Yashamaru, a part of Gaara still wanted to have bonds, because if that want wasn't there in the first place, there would have been nothing for Naruto-kun to get to, in the Forest when he protected his team from Gaara, and later in the fight. If that want of loving bonds where there in the first place, then that thing with Gai-sensei and Lee wouldn't have got to him so much, that emotional slap in the face he got in the arena, when he saw how Lee had the love of a teacher when his own father wants him dead, when in fact, his father had sent him to Konoha to die.
Everytime Gaara sleeps, Shukaku eats at his sanity, and I get the feeling that this is something that Gaara is deeply afraid of. It was mention much later, like when Naruto was losing control and Nine-Tails chakra started leaking after they retrieved Gaara's body in the forest, that if it wasn't stopped, Nine-Tails will take over, and I think Naruto would die? Whether Gaara would actually die (or rather, whether his body will die), by ordering Gaara to let Shukaku take the wheels (and KEEP the wheels), the Yondaime Kazekage had sent 12 year old Gaara out to die, and the people around him went along with it.
This is why Gaara got so much more unstable during the Chunnin exam, and I think this explains his sibling's behaviour as well, which always had of guilt and longing mixed in. This was a part of Kankuro's anger at the elders in Part II as well, he's getting so angry then because he didn't speak out before.