I never thought of it as an ability to make people go to sleep, but I have been told that my presence and voice has a very soothing effect on people.
When I was in high school I was a youth camp leader at a girls summer camp. my first year as a YCL, I was given the task of telling bedtime stories to the younger girls to help them adjust to being away from home for the first time. Apparently I was successful in comforting them, because every summer I went back there, I was bombarded with requests from the younger girls to come tell them stories, and sing to them before they went to sleep each night. My last year there, more than half the campsite turned up for my stories, packing the first year cabin full.
maybe it really does have something to do with the personality type