(21+ content is possible and widely used in The Sims community)
Most of these modifications fit the ESRB 'T for Teen' /PEGI-12 rating of the game, but some mods are more 18+. If you are a parent of an underage teen player of The Sims 3, you should be aware that the player community has developed many modifications to the game that are easy to find by anyone who can use Google to search the web.
