Of Cassander's sons, the elder, Antipater, killed his mother Thessalonicé and drove away his brother Alexander.
Edition :
Plutarch Lives IX: Demetrius and Antony, Pyrrhus and Caius Marius, Ed. Jeffrey Henderson, trans. Bernadotte Perrin (The Loeb Classical Library 101), Harvard University Press: Cambridge/MA - London 1968 (first ed. 1920).
Remark :
motive: The motive is political because Antipater killed her to achieve sole control over Macedonia, according to the New Pauly.
http://referenceworks.brillonline.com/entries/brill-s-new-pauly/thessalonica-e1210990 long-term consequence: Alexander calls on Pyrrhus and Demetrius for help and Pyrrhus defeats Antipater in war. This is mentioned in 6.3.