Macbeth Act 3, Scene 1

Macbeth is concerned about Banquo. He is thinking it is best to have him and his son killed so that they cannot interfere with his power. Macbeth is well aware of the prophecy he received compared to the one Banquo received. He concludes that Banquo and his son are a threat because the witches predicted Banquo fathering kings. Macbeth may have been predicted to be king, but he will not father any. That could very well mean that Macbeth will only be in power for a short time. He is trying to make sure that he can stay in control and protect himself from his enemies. His safety is his main concern at this time.