What does "who" refer to? "one of them" or just "them"?
In the sentence "Whenever I met one of them who seemed to me at all clear-sighted, I tried...", what does "who" refer to? "one of them" or just "them"?

In the course of this life, I have had a great many encounters with a great many people who have been concerned with matters of consequence. I have lived a great deal among grown-ups. I have seen them intimately, close at hand. And that hasn't much improved my opinion of them.
Whenever I met one of them who seemed to me at all clear-sighted, I tried the experiment of showing him my Drawing Number one, which I have always kept.

Question

What does "who" refer to? "one of them" or just "them"?
In the sentence "Whenever I met one of them who seemed to me at all clear-sighted, I tried...", what does "who" refer to? "one of them" or just "them"?

In  the course of this life, I have had a great many encounters with a great many people who have been concerned with matters of consequence. I have lived a great deal among grown-ups. I have seen them intimately, close at hand. And that hasn't much improved my opinion of them. 
Whenever I met one of them who seemed to me at all clear-sighted, I tried the experiment of showing him my Drawing Number one, which I have always kept.

Answer

Hi!
It refers to "one of them".
The author has met many grownups.
Out of all of these grownups he has met, whenever one seemed clear-sighted, the author would show the grown-up Drawing Number One.

Answer

The “who” is referring to “one of them” because the object is “one of them” as a phrase and not only “them.” Another thing that can help is in the following sentence that goes “... showing him...” and we can understand that he is talking about one person.
Hopefully this helps!

Ps. I love The Little Prince!