When I was 10 and my brother David was seven, my parents took on a local neighbourhood girl called Linda to babysit us occasionally when they went out. Linda was 16 or 17, I think, extremely pretty and I knew her younger brother fairly well, who would be a couple of years older than myself.
I have very good cause to remember the first time Linda looked after us because it ended up in a memorable sore bottom for both myself and my brother.