It seems like the intended meaning of "why deny the obvious child" changes throughout the song, as the character's life changes. What's obvious to the man (and sonny, who I interpretted as actually being his son and repeating the cycle of aging and midlife crisis-ing) changes, as does his "cross," the burden he has to carry through life. I think this is true of a lot of Paul Simon's songs - he seems to use a lot of visually descriptive lyrics, and repeats choruses that seem to mean different things along the way but somehow tie together in a way that listeners can feel what he means, yet none of us can really pin it down. Probably what makes his songs so enjoyable - at least for me, personally.
It seems like the intended meaning of "why deny the obvious child" changes throughout the song, as the character's life changes. What's obvious to the man (and sonny, who I interpretted as actually being his son and repeating the cycle of aging and midlife crisis-ing) changes, as does his "cross," the burden he has to carry through life. I think this is true of a lot of Paul Simon's songs - he seems to use a lot of visually descriptive lyrics, and repeats choruses that seem to mean different things along the way but somehow tie together in a way that listeners can feel what he means, yet none of us can really pin it down. Probably what makes his songs so enjoyable - at least for me, personally.