Can I refer my sibling for a PhD position under my supervisor? How should I approach this?
I would worry a bit about asking the professor to &quot;hire&quot; your sibling. On the other hand, telling the professor that your sib is looking for a position in the same field and would like to meet them to talk about the possibilities would be entirely appropriate.
If the two of them, without you, come to some understanding it would be better. And even if that isn't possible, the prof may have some good ideas for your sibling to pursue.
So, I'd suggest a somewhat less direct approach.