Strong’s Greek
G3995 — pentheros
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
πενθερός
pentheros — pronounced pen-ther-os'
of uncertain affinity; a wife's father:--father in law.
1 occurrence in the KJV.
John 18:13
And led him away to Annas first; for he was father in law to Caiaphas, which was the high priest that same year.