This is sad all around. The 10 year old could of learned that anywhere from her mom having lots of "boyfriends" over, a older brother watching porn and leaving the video open or from fresh kids at school.
The 10 year old will be demonized and life ruined while the toddler scarred sexually and having screwed up relationships potentially rape others as well. I hate to throw the race card but lil Becky would of got the "She saw this on TV and was just being curious. Lets get her a counselor" treatment.