I'd heard the rule (if it really is one; it might be more of a convention) that the pronoun would refer to the subject of the previous clause or sentence, in which case the subject would be the brother and not the vicar. The confusion is when the passive voice is introduced. In the active voice, the problem evaporates: "On my way home from school, the town vicar chased my brother. He'd heard about the catechism class vaping ring." Consider this : "Mr Harvey gave the fishmonger only sixpence for the fish. He didn't have any more." Clearly, it was Mr Harvey who didn't have more, not the fishmonger or the fish. but recast the sentence in the passive voice, and the confusion returns: "The fishmonger was given only sixpence by Mr Harvey for the fish. He didn't have any more." How true. That is what bedevils writers. I think it was Cicero who said that it is not enough to be understood, but to make it impossible to be misunderstood. Or, in other words, if there's any way to make a sentence clearer, go for it. Your reader will thank you.