infant prodigy vs youngster

infant prodigy and youngster both are nouns.

Word	Noun	Adjective	Verb	Adverb
infant prodigy	Yes	No	No	No
youngster	Yes	No	No	No

As nouns, youngster is a hypernym of infant prodigy; that is, youngster is a word with a broader meaning than infant prodigy:

Other hypernyms of infant prodigy include child, fry, kid, minor, nestling, nipper, shaver, small fry, tiddler, tike, tyke, prodigy.

infant prodigy (noun)	youngster (noun)
a prodigy whose talents are recognized at an early age	a young person of either sex