Instructions
Download the Inteen3 file from a modification website, such as ModTheSims.info, SexySims2.com or MoreAwesomeThanYou.com. Select "Save to Desktop" when prompted.
Right-click the icon and select "Extract to Desktop."
Open "My Computer" and "Drive C." Select "Program Files," "Electronic Arts" and "The Sims 3."
Click on the "Mods" folder and "Packages." Drag the Inteen3 file from your desktop into this folder.
Launch "The Sims 3" game and wait for a file to load. Once the game starts, teenagers will have the same relationship options as adults.