Yep, they definitely suspect it. Orphell thought that Rood could be Kiel's brother until he learned that Mikel killed the brother. Although I don't think he is completely convinced that Rood and Kiel are not related. But combined with his questionable experiences with Rood at school, he now should definitely suspect that he is the BM. Especially since he, as a student, used the technique of an official magician - successfully.
And Mikel ordered Kiel to prove that Rood is not the BM, but I have no idea what Kiel is planning to do. According to his orders Rood should be allowed to transform now, but I guess he will understand that it is NOT a good idea to do so in front of Mikel when his "master" doesn't pose a real danger to him and his teammates.