Closest family member (4,2,3)
I believe the answer is:
next of kin
'closest family member' is the definition.
(I know that closest family member can be written as next of kin)
This is all the clue.
(Other definitions for next of kin that I've seen before include "Nearest relatives" , "Closest living relative" , "One's closest relatives" , "nearest people" .)