without natural affection

Concise Bible Dictionary:

That which is according to nature.

Strong’s Dictionary of Greek Words:

Greek:
ἄστοργος
Transliteration:
astorgos
Phonic:
as’-tor-gos
Meaning:
from 1 (as a negative particle) and a presumed derivative of στέργω (to cherish affectionately); hard-hearted towards kindred
KJV Usage:
without natural affection