He doesn't tell her about his plans to murder Banquo and Fleance because he wants it to be a nice surprise for her. Yeah, it's crazy, but he's seriously sleep-deprived.
Banquo probably doen't know for sure about how Macbeth is planning on killing Duncan so he can become king. Even if Banquo did know, he is a very loyal friend to Macbeth and will keep all of his suspicions to himself. Which is ironic, because Mabeth ends up hiring murderers to kill Banquo, which goes to show you that Macbeth really isn't that loyal.
*Banquo. Macbeth's best friend is Banquo, but he is also Macbeth's enemy. After the meeting with the witches, Macbeth finds out that he will become the Thane of Cawdor and the King of Scotland. Eventually, he achieves both of these prophecies. Banquo, Macbeth, and Lady Macbeth are the only people that know about the witches. Banquo becomes suspicious of Macbeth because Macbeth fulfills the prophecy after King Duncan is murdered, and Macbeth acknowledges this fact. Basically, Macbeth doesn't trust Banquo.
Macbeth doesn't really have a conflict with them. Banquo suspects Macbeth of killing Duncan, but isn't saying anything. Macbeth is annoyed by the witches' prediction that his children will not succeed him (Does he have children? The way things are going between him and his wife, is it likely that he will?) but that Banquo's decendants will. He is jealous. Macbeth's murder of Banquo and attempt on Fleance's life are an attempt to prove to himself that his future is not controlled, and that he is free. He wants to know that he became king because of what he did, not some inexorable fate. When the murderers fail to kill Fleance, he says, "Then comes my fit again!". He has not proven that he is free. The witches' predictions about Banquo can come true. Maybe it is all a matter of fate after all.
because he just knows
Banquo's lines about the star's recall reflect his suspicion towards Macbeth's sudden rise to power after the witches' prophecy. Earlier, Banquo had warned Macbeth about the deceptive nature of the witches and their prophecies, suggesting that they might lead to harm or destruction. This sets up Banquo as a foil to Macbeth, highlighting his moral integrity and skepticism compared to Macbeth's ambitious and deceitful nature.
If he did, it is not shown in the play. As far as we know, he only had the one chance encounter with them.
I would say, Banquo had will. His will out weighed any temptations he had towards his goals. Though, just as ambitious as Macbeth, Banquo held back, happy to sit in the back seat as Macbeth explored the front row. This, truthfully would have been better in the long run (you know what they say about the tortoise and the hare) if it wasn't for Macbeth's greed and paranoia.
Lady Macbeth wasn't in on her husband's plans to kill Banquo. When she asked what his plans 'of dreadful note' [Act 3 Scene 2 Line 44] were, he didn't want her to know the specifics. But most likely yes, she would have wanted Macbeth to kill Banquo. Earlier in their conversation, she commented that Banquo and his son Fleance were mortal [and therefore killable?].
The general opinion is that his sons Malcolm and Donalbain had hired his grooms to kill their father. This was supposedly proven because they took off after the murder was discovered, a sign of guilt. This is explained by Macduff in Act II Scene 4.
Macbeth wants Banquo dead because Banquo witnessed what the three witches said. The three witches stated that Macbeth would one day become king. Now that Macbeth has become king, and done so by taking the life of the previous King Duncan, he fears that Banquo will spread the word that Macbeth was the one to commit the murder.
He asked for it. ("Shall Banquo's issue ever reign in this kingdom?") The witches even tried to talk him out of it ("Seek to know no more") but he insists ("Deny me this and an eternal curse fall on you.")
i think Macbeth wanted to be king. he couldn't though because king Duncan was. So Macbeth killed him. Then Banqou was suppose to be next to be kind, i believe. So he hired the revengers or avengers to murder him. Next was fleance. i don't know what happened to him.