Which brother cares the most? Loki or Thor?Watch
Only because, they seemed to get on fine until Loki found out he was adopted in Thor 1. Then all the bitter resentment was shifted from Odin onto Thor. I wouldn't say Loki doesn't love his brother, because although he often betrays Thor and looks out for himself, he sacrificed his beloved Tesseract for his brother's head, I mean c'mon!
Loki can love his brother, he just can't, his childhood issues and growing up the second have become a breeding ground for negative thoughts and a feeling that he will never be important, at the top of all this is Thor, the root of his negativity, so it is hardly a task to explain why Loki chooses not to love his brother.
I think you can tell I dont like Thor's buddies very much!
I think Thor finds it hard to understand Loki because Loki isolates himself a lot. And also Thor used to leave Loki out all the time as kids, having sleepovers with the Warriors three!
(MTV after hours w/ Tom Hiddleston reference)