in the middle

It's known that I like to guess people's Myers Briggs letters... I can't help it, it is subconscious really, happening under the surface of my in-the-moment interactions with each new or not-so-new person I meet. It's not with everyone, everytime, but often. But I can be pretty wrong sometimes. Meanwhile, I'm trying a new method of understanding people a little better... much simpler, easier to figure out immediately, and doesn't reveal how much of a psychology nerd I am...

He stood by the entrance to the dressing room, among the headbands and necklaces of the girls section. He was so patient, waiting around for us girls as we shopped and tried things on. Very much a gentleman, this guy, also extremely stylish, but with an ever-so-slight air of being out of his comfort zone, laughing a bit at the girlishness all around him. I paused whatever else we were talking about and asked him, "Do you not have any sisters?"
"No," he laughed. "I don't. I have two brothers, and my mother is not very girly at all."
"So there's three boys then," I confirmed, and he nodded. "So, are you the middle brother?"
He tilted his head in a bit of surprise, and said, "Yeah, I am! How did you guess?"

Then I felt a little hesitant, I haven't really done such a direct and accurate guess before with someone I have known such a short time. I didn't know how to answer without giving away that I am maybe too observant and then too quick to categorize my information. But he had some really precise personal qualities, ones that didn't only speak to being Scandinavian. He was very neat and organized and disciplined and driven but laid-back and somewhat spontaneous. He was a friend of my friend, and had been the best host to four girls he didn't really know...preparing amazing cocktails, buying magazines in case we wanted to read by the pool, and making gourmet sandwiches for everyone at 3 am.

"Well, I don't know, I just kinda like guessing sibling order, it's a thing I do," I tried to shrug off the responsibility of an answer.
"No come on, you must have reasons behind your guesses! Why did you say the middle?" he pushed. I tried one more time to evade him, he wasn't having it.
"Okay, well you are organized and put-together, ambitious I think, and are good at directing a group. The youngest sibling tends to not have all those qualities, but the oldest would have more of a bossy element to them, less people-pleasing, not quite as mellow as you. So that's why I wouldn't have gone for oldest either."
"You are pretty right, I would say," he said with an amused smile. I don't think everyone likes the feeling that someone is looking deeper than the momentary interactions with them. I know not everyone does. And I know I will be wrong as often as I am right. But I love that moment when someone is pleasantly surprised by it. To those who feel unsettled by feeling known, even a little, I'll try to keep my mouth shut.