I noticed that the same Alliance always attack the same castle... I kind of wonder whether that was..

Those are farm accounts for players. They are to provide extra resources (rss) for that player by plundering it with their main account.

I'm not sure if it is that way some of the time, but I get attacked at least twice or three times a day by the same people. My castle level is nine below theirs, and my alliance mate is also attacked continuously. I wish there was a cap on the number of times a person can be attacked by an individual in a week. It would be nice to at least heal my wounded before they come in to plunder. I have nothing for them as the little I have goes into healing. I don't know if it is part of the game or if it is a bully tactic. It isn't fun, and I've considered quitting the game.