Hi,
I wonder if you find the following valid: “All the questions concerning who with/how/for how long could be nested within a core one: Why?”
I find the meaning very unclear, and if you mean this:
All the questions concerning the ideas ‘who?’, ‘with?’, ‘how?’, ‘for how long?’ could be nested within a core one: ‘Why?’
then I would say it is not the case.
What was meant was not questions, Bev, rather animated ones. Before you take decision on who with…/for how long (you want to live) you have to answer a simple Why? (= are they worth it/are you a match?). Just idle thinking… 
Then it’s unclear. I suggest:
When it comes to personal relationships, all the questions concerning ‘who with?’, ‘how?’, ‘for how long?’ could be nested within a core thought: ‘Why?’
Yes, I agree, Bev, it wasn’t easy to catch on without a context.
like the intersection of roads llike where two roads meet. what is it called
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=A crossroads if the roads cross.
A T junction if they roughly form a T shape when viewed from above.
A junction (largely BrE) or intersection (largely AmE) if neither of the above applies.