Other hyponyms of youngster include
buster,
changeling,
child prodigy,
infant prodigy,
wonder child,
foster-child,
foster child,
fosterling,
imp,
monkey,
rapscallion,
rascal,
scalawag,
scallywag,
scamp,
kiddie,
kiddy,
orphan,
peanut,
picaninny,
piccaninny,
pickaninny,
poster child,
kindergartener,
kindergartner,
preschooler,
silly,
sprog,
bambino,
toddler,
tot,
yearling,
urchin,
street child,
waif.