Student sequel

I have a sweet follow-up to the post I wrote about my student who comes from a family of five children. See: ("the subtleties of kid counting") He was again in my office two days ago, discussing his final essay draft, in which he compared a Langston Hughes poem, "Mother to Son," to his own mother and the relationship he has with her. In the assignment, he notes that his mother had a child later in life, when most of her friends were well beyond their child-bearing years. This, of course, caused me pause, because my own mother had me when she was 42. (See the essay that spawned the blog: "An essay on the origins of the kid counting fascination")

"Are you this youngest child?" I asked my student, holding my finger on the sentence where I'd left off reading.
"Yeah," he responded, barely looking up.
"How old was your Mom when she had you?"
"45," he replied, raising his chin.
"Really? My Mom was 42 when she had me," I said, with, perhaps, a little too much enthusiasm in my voice. "And, I'm also the youngest of five," I added, without thinking.
I'd slipped.
He looked up at me, confused, his eyes saying, quite clearly: how do you, my dear English professor, know how many siblings I have?
I'm a kid counter, I could have told him, and maybe I should have. Family size is certainly a topic I would have liked to bat around with him. But instead, before he had a chance to utter a word, I told him I remembered his sibling kid count from one of his in-class writings (which is true, I'll have you know). He seemed perplexed, but satisfied, and maybe even impressed.
"How far apart are you from your next closest sibling?" I asked, breaking the moment of perceived awkwardness.
"Eighteen years."
Wow. There's a first. I've never met someone with a family dynamic so similar to my own. When I was born, my siblings were 16, 18, 20 and 22. When he was born, his were 18, 20, 22, and 24. I was, as you might suspect, dying to ask him more, more about how it was for him growing up, more about how well he knew his siblings and their children, more about how he felt about having older parents. But I didn't. We had an essay to edit, I had a nanny to relieve and an afternoon to spend outdoors (or indoors as the weather then dictated) with my sons. What I would have asked first, had it been more appropriate, was "Do you, 20-year-old you, imagine having a big family yourself?"