Grimms' Fairy Tales
How we cite our quotes:
Since Unfaithful Ferdinand kept a grudge against Faithful Ferdinand, and since he also kept hearing the king lament, he finally said, "You have the outrider, don't you? Well, why don't you send him to find her, and if he doesn't bring her back, have him beheaded." (Faithful Ferdinand and Unfaithful Ferdinand.412)
Obviously someone with your name will betray you. There can be only one.
Now Hans put the maiden into the basket and ordered his companions to pull her up. The basket came down again, but Hans did not trust his two companions and thought, They have already shown themselves to be untrustworthy by not telling you about the dwarf. Who knows what they have up their sleeve now? So he put his staff into the basket, and it was lucky he did this, for they let the basket drop when it was halfway up, and if Hans had really been sitting in it, he would have died. (Strong Hans.497-498)
Hans didn't give his companions any reason to betray him, but they did so because they felt jealous and threatened. Jealousy seems to be a major divisive force in these tales, doesn't it? It sure does explain why a lot of folks betray people they should definitely be loyal to.
The sparrow realized that the wagon was heading straight down the lane in which the dog was lying and that it was not going to swerve. "Wagoner, don't do that, or I'll make you a poor man!" the sparrow cried out. "You won't make me poor!" the wagoner bellowed as he whipped the horses and drove the wagon over the dog, killing him with the wheels. (The Dog and the Sparrow.205)
Interspecies friendships are the best. And the most vengeful. The sparrow goes on to wreak havoc on the wagoner's life, including killing him. So the loyalty of even small critters shouldn't be discounted.