When I was 6, I got lifted by a little girl at same age in kindergarten. She was one of the biggest kids in our "class" and she lifted me once by surprise from behind (her front to my back). I felt aroused and got an erection, but I was't aware back then what was that, and it wasn't something I was concerned about. That was not a first time for me to get en erection.
I don't know that woman today, but I saw her father two years ago and he told me she is a scientist now.
When I was 8-11 I was often playing around with my neighbors at similar age. We used to climb on trees and lifting each other to reach high branches from a ground level. It was no matter who was boy or girl and then I never get hard when being lifted by a female friend in such a conditions. It was not sexual thing for me back then, and I haven't even heard about sex before i turned 12.
In high school I was one of the smallest and skinniest people in my class (I was a little late with body growth at my teenage, I looked like a 12 yo when I was 17). Once, when I was sitting in a frame of opened window during a break, my big breasted female classmate(who looked like a real woman) offered me to lift me in a cradle, but I refused because it was a taboo for me back then. I was thinking she can't do that.
I was about 5' 8'' / 143 and she was an inch or two shorter and about 150 lbs.
A few years later I start digging the internet in a search for some kinky sexual pictures or videos and so I found one picture of a girl in sexy white lingerie holding in a cradle another girl about same size in a matched dark blue lingerie. I liked the picture much.
After I got married, I got lifted once in an everyday situation barely off the ground by my wife and I get very excited. I think this is my real start with a l&c fetish. My wife like to lift and carry me and also to be lifted and carried by me. We do it from time to time. I must say I am still in a small frame, but not so small as I was in my late teenage. I am only 6' tall / 185 lbs for a male and my wife is in very small frame at 5' 2'' / 120 lbs, for a female.
So, I really started to be interested for l&c stuff in my early 20-s and start practicing it in real life in my late 20-s.