The three conjoined Fates were begotten by Erebus on Night, their names are Clotho, Lachesis and Atropos. Zeus weighs the lives of men and informs the Fates so that the thread of life, spun on Clotho's spindle and measured by the rod of Lachesis, can be snipped by Atropos' shears. Some hold that even Zeus is subject to the Fates, because they are not his children, but parthenogenous daughters of the Great Goddess Necessity, who is called The Strong Fate.
Robert Graves, The Greek Myths. Complete Edition.