It was absolutely a thing that people engaged in intergenerational affairs, even between adults and minors. I know that this is unacceptable by today's standards, but people in the 1970s did not live by today's standards ( very far from it!), and each side of such intergenerational pairs would be both proud and boastful of their relationship.
Sorry if it upsets your present-day worldview, but that was absolutely the zeitgeist of the 1970s, as creepy as some of it seems now (and deservedly so).
For a good film of (some of) things were back then, view Ang Lee's "The Ice Storm" - it really is representative of middle and upper-middle-class surbaban USA in the 1970s.
Sorry if it upsets your present-day worldview, but that was absolutely the zeitgeist of the 1970s, as creepy as some of it seems now (and deservedly so).
For a good film of (some of) things were back then, view Ang Lee's "The Ice Storm" - it really is representative of middle and upper-middle-class surbaban USA in the 1970s.