Sister's son, say (6)
I believe the answer is:
nephew
(Other definitions for nephew that I've seen before include "Brother's/sister's son" , "A sibling's child" , "Sister's son" , "Sibling's son" , "Male relative" .)
I believe the answer is:
nephew
(Other definitions for nephew that I've seen before include "Brother's/sister's son" , "A sibling's child" , "Sister's son" , "Sibling's son" , "Male relative" .)