Well, I haven't studied long enough Leonard's lyrics (as I intend to) but I can get a shallow glimpse of what "First..." might be about.
The sure thing is that it is somehow related to the Eastern German terrorist factions. But that won't sufficient to explain the whole of the song. Well, you should also consider Hydrot that in the moment of writing, and specifically when writing poetry, the amount of connections you make between several elements of your experience are so vast that the finalized "product" isn't only explainable by the examination of it's parts. In the literary process, you end up creating from many different matrixes the piece, but this selection isn't completely at random neither is completely at will. The author will include his own experiences and somehow relate completely different topics in the same creation, and somehow, by a process I really don't want to understand because I personally feel it completely blows the miracle of the arts, these opposite topics find a way to encounter things in common.
So, the sister whose demise becomes so painful to the speaker may have something to do with the image industry, with it's diet pills, it's focus on youth and physical beauty. Youth and physical beauty which are so deeply embedded on the hearts and minds of the wild spirited radicals who join groups like the Baader-Meinhoff, or The Red Army, or the IRA, etc. People who dream large, whose desire to seize all those glorious youthful sensations into a single blow, taking it a city at a time. And these people are determined, feeling as though they we're destined, guided by a signal in the heavens People with large idealism, in love with the feelings, in love with the arts, who wanna live through them Who get other youngsters like them to fall deeply in love, who like them as they are when they are bearded, smooth looking rebels, with no steady income, but who turn their backs the minute that handsome rebel accomplishes some of his/her dreams. ... And they do something awful, get thrown in jail, and they lose complete track of where their lives are headed to....
This is a very literal approximation if you want the truth. But I think that's where the whole point of the song lies. It's about the deception the person feels as time strikes them, as they see their ideals gone through the not very gold plated toilet of history. And, too, when they see the things they weren't quite right about, yet, they are too cynical now to feel remorse or to head themselves in another direction, just living for the day's end. I like to think that's what LC had in mind when writing this... just as I like to think all the revolutionary birds from the 60's 70' feel nowadays, looking back as to how things ended up, not quite as lovely as they wanted, not quite as clean as their movement wanted to move.
So, at in the end, the poem itself is a "matrix" where you put your own perspective, and you come out with your own interpretation afterwards. The whole point about poetry and literature is that it give a way wider margin of freedom to interpretate what you may want, and that way, repeat the same process the author deploys in the creation of the work. And the better the work is, the more the meaningful and insightful interpretations.
And don't forget to just enjoy it for a while, It's only poetry but it feels so good.