ball boy vs male child

ball boy and male child both are nouns.

Word	Noun	Adjective	Verb	Adverb
ball boy	Yes	No	No	No
male child	Yes	No	No	No

As nouns, male child is a hypernym of ball boy; that is, male child is a word with a broader meaning than ball boy:

Other hypernyms of ball boy include boy.

ball boy (noun)	male child (noun)
a boy who retrieves balls for tennis players	a youthful male person