Essentially, the similarities between the deaths of Duncan, his guards, Banquo and Macduff'f family, as seen in William Shakespeare's Macbeth, have one resounding tie: they all lose their lives based upon Macbeth's ambition.
Duncan and his guards die for one reason: Macbeth desires the crown. Since hearing the prophecy of the witches, Macbeth's ambitious nature has compounded. He will no longer allow fate to make the moves:
If chance will have me king, why, chance
may crown me
Without my stir.
The guards die so that Macbeth can place blame on someone other than himself. Duncan dies so that Macbeth can have the throne.
As for Banquo's and Macduff's family, their murders are a part of Macbeth's plan to keep the throne. Macbeth knows that Banquo is a threat based upon the fact that he witnessed the prophecy. Known by readers but not by Macbeth, Banquo does believe that Macbeth may have had something to do with Duncan's death.
Thou hast it now: King, Cawdor, Glamis, all,
As the weird women promised, and I fear
Thou play'dst most foully for't.
Also, Macbeth fears that another part of the prophecy will come true: Banquo's sons will be kings. By this, Macbeth believes that he will lose the throne to Banquo's sons. Therefore, by trying to murder Fleance, and murdering Banquo, the likeliness of the prophecy coming true is lessened.
Like Banquo's murder, the murder of the Macduff family is meant to insure Macbeth keeps the crown. He believes that Macduff will try to kill him (again foreseen by the prophetic witches and the apparitions).
Macbeth! Macbeth! Macbeth! Beware
Beware the Thane of Fife. Dismiss me. Enough.
Therefore, Macbeth sends the murderers to kill Macduff (unaware that he has fled). Instead, the murderers kill Macduff's family.
They were all struck for thee! Naught that I am,
Not for their own demerits, but for mine,
Fell slaughter on their souls. Heaven rest them now!
In the end, all of the characters (Duncan, his guards, Banquo, and Macduff's family) are murdered to insure the throne for Macbeth.
It is usually said that all the victims of Macbeth are merciless preys of Macbeth's motiveless malignity. But this is far from the truth. Duncan was murdered to pave way for Macbeth's ascension to the throne. The grooms were murdered with a motive too- to hide them from publicly averring their innocence and to pass the onus of the crime to those guards who macbeth smears with blood. Banquo and his son were also murdered with a motive. Macbeth, rapt in the prophecy of the witches, was more after fleance than after banquo. But keeping banquo alive kept the possibility of his progeny to wrench the throne in future from Macbeth. thus to make his throne safe from the successors of banquo, both needed to be erased from the living world. Lady Macduff's murder and the brutal slaughter of her son was also motivated by revenge, triggered bytwo factors- first, the witches's prophecy of being wary of Macduff, the greatest mortal enemy of macbeth, as decreed by fate, and second, his sudden fury against Macduff at the realization that by not attending the banquet, Macduff had defied him,
What then is common in all these murders where the motives were all different. The common issue is that all the victims are innocent people who have done the villain-hero no harm, and these cumulative murders serve to undersore the criminal nature of Macbeth. These murders were not common in their motivation for actualizing the leaping ambition of Macbeth, but to throw light, over and over again, upon the gruesome murderous evil that ruled the life of Macbeth.
Umm, that they were all killed in cold blood and were killed without any reason? Although Macbeth has his reasons to kill them, there was always a big IF.