You certaintly didn't search too well, then. Here some citations:
"Thanatos was loosely associated with the three Moirai (for Hesiod, also daughters of Night), particularly Atropos, who was a goddess of death in her own right. He is also occasionally specified as being exclusive to peaceful death, while the bloodthirsty Keres embodied violent death."
"THANATOS was the god or personified spirit (daimon) of non-violent death. His touch was gentle, likened to that of his twin brother Hypnos (Sleep). Violent death was the domain of Thanatos' blood-craving sisters, the Keres, spirits of slaughter and disease."