This happened to me recently and I don't want to spoil things up, since I am sharing my personal story in a long posting, but I never thought the joy of binging and kidnaping play will lead me to the most unexpected person.
When I was 8 or 9 I was playing mommy/baby with my toddler sister and put her up to my nipple (didn't have breasts).
It gave me a pleasurable feeling I didn't understand and I had her continue for some minutes. Never repeated.
The first time I had something like lesbian sex was with a friend when we were about 4. Then when I was 7, it happened again with a different friend. In both cases they inititated... bet they're married now though and forgot all about it.