Learn English – Term for: Looking at someone like they’re stupid

I think you can describe the relationship as brotherly or fraternal suggesting that they are like brothers:

• of, resembling, or suitable to a brother, esp in showing loyalty and affection; fraternal. (Collins)

Given the context described and the fraternal relationship, the younger man could be referred to as the policeman's little brother:

• A close male friend; (AHD)

You may be referring to prefiguration, which is a typology primarily used in theology?

Typology in Christian theology and Biblical exegesis is a doctrine or theory concerning the relationship of the Old Testament to the New Testament. Events, persons, or statements in the Old Testament are seen as types pre-figuring or superseded by antitypes, events or aspects of Christ or his revelation described in the New Testament. For example, Jonah may be seen as the type of Christ in that he emerged from the fish's belly and thus appeared to rise from death.

Source: Wiki

Otherwise, foreshadowing is probably the closest match.