What does Macbeth mean when he says “We hear our bloody cousins are bestowed in England and Ireland not confessing their parricide, filling...

This quote is from Act III, Scene 1 of Macbeth. Macbeth is speaking here to Banquo, and when he says "bloody cousins," he is referring to Malcolm and Donalbain, the sons of the murdered King Duncan. By using the adjective "bloody," he suggests that it is they who murdered the king. This, he and others have already said in the play, is why they must have fled to England and Ireland, respectively, in the first place. Of course, Malcolm and his younger brother Donalbain, Macbeth tells Banquo, are refusing to confess their involvement in the murder (which, the audience knows, Macbeth was actually responsible for). But even worse, they are involved in "strange invention," or spreading stories about the murder. We can assume, based on context, that they are rallying opposition to Macbeth by telling the truth—that he is Duncan's murderer. Macbeth correctly perceives this as a threat to his power.