"Child labor" is, generally speaking, work for children that harms them or exploits them in some way (physically, mentally, morally, or by blocking access to education).
A grandfather generally would not be exploited in child labor.
( z1 exploit :polarity - :ARG0 ( z2 labor :ARG0 ( z3 child ) ) :ARG1 ( z4 person :ARG0-of ( z5 have-rel-role :ARG2 ( z6 grandfather ) ) ) :ARG1-of ( z7 general ) )