Yeah, in the original mythology they aren't considered brothers. Actually Odin and Loki are brothers after Odin tricked Loki (I know right, ironic) into becoming "blood brothers" through ritual. But Thor basically hates Loki throughout the mythos (especially when Loki cuts off his wife's hair but we don't talk about that)

But I am totally fine if we don't stick with the original mythos because it can get [i]complicated[/i] lol.