I'm going to assume the thief is part of the plan, because he'd be an idiot otherwise. Also, the fact that Aidra was sent back before she was married makes sense now.
@rei893 No, the earlier chapter said that the wedding was delayed again and again until the princess came back with her baby later on, without having married. So basically everyone pretty much knew she got pregnant by someone else. It would make no sense for Kaldus Coendera to send her away if she was preggers with his baby.