In a barbaric era, population pressures made war and even the slaughter of one community by another a fact of life. Survival depended in having a capable warlord to protect life and property, prevent infighting, and protect from distant enemies. Groups of warlords would unite under the nominal leadership of one king to promote their common interests and war on more distant nations. While people pretended to believe in "the divine right of kings" and "lawful succession", continuing effective leadership was assured by warlords killing off the less capable family members.
The name "Macbeth" means "son of life", and is a Christian name rather than a patronymic (hence the "b" is lower case.) Macbeth would have signed his friends' high school yearbooks "Macbeth mac Findlaech" (McFinley). There are MacBeth families in Scotland and Nova Scotia.
Macbeth's father Findlaech was ruler ("mormaer", high steward) of Moray, at the northern tip of Scotland. Macbeth's mother's name is unknown, but she is variously said to have been the daughter of King Kenneth II or the daughter of King Malcolm II. In 1020, Findlaech was killed and succeeded by his nephew Gillacomgain. In 1032, Gillacomgain and fifty other people were burned to death in retribution for the murder of Findlaech, probably by Macbeth and allies.
The historical Mrs. Macbeth was not named "Lady", but "Gruoch" (GROO-och). She was the daughter of a man named Biote (Beoedhe), who was in turn the son of King Kenneth III "the Grim" who Malcolm II had killed to become king. (Some say that Biote was the son of Kenneth II instead.) She was originally married to Gillacomgain. Their son was Lulach the Simple (i.e., stupid; no, Lady Macbeth didn't brain him.) After Macbeth killed Gillacomgain, he took his widow Gruoch for his own wife, and raised Lulach as their stepson. What a