Strong’s Greek
G431 — anepsios
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
ἀνεψιός
anepsios — pronounced an-eps'-ee-os
from 1 (as a particle of union) and an obsolete nepos (a brood); properly, akin, i.e. (specially) a cousin:--sister's son. see GREEK for 1
1 occurrence in the KJV.
Colossians 4:10
Aristarchus my fellowprisoner saluteth you, and Marcus, sister’s son to Barnabas, (touching whom ye received commandments: if he come unto you, receive him;)