marriage broker vs go-between

marriage broker and go-between both are nouns.

Word	Noun	Adjective	Verb	Adverb
marriage broker	Yes	No	No	No
go-between	Yes	No	No	No

As nouns, go-between is a hypernym of marriage broker; that is, go-between is a word with a broader meaning than marriage broker:

marriage broker: someone who arranges (or tries to arrange) marriages for others
go-between: a negotiator who acts as a link between parties

Other hypernyms of marriage broker include intercessor, intermediary, intermediator, mediator.

marriage broker (noun)	go-between (noun)
someone who arranges (or tries to arrange) marriages for others	a negotiator who acts as a link between parties