@mboog,
Yes, whom is correct. I always think... Is the person doing anything? Or is someone doing something to him?
Ex: Immediately suspicious of her brother, who had a suspecting sister...
Immediately suspicious of her brother, whom she supposed it was...
Notice how, in the first one, her brother had something? Therefore, he is the subject. In the second one, someone supposed it was him. He's the object there. Hope I helped!