How to Get Relatives to Kiss in "the Sims 3"by Seth Amery ; Updated September 22, 2017
By default, relatives are off-limits as romantic interests in "The Sims 3" due to fellow Sims considering the act taboo. That doesn't mean you can't still bypass in-game restrictions with the use of a mod. Traditionally a mod to enhance missing romance features, the WooHooer mod features a setting where you can modify restrictions on close relationships with family members.
Download and install the WooHooer mod by NRaas. The mod archive uses a one-size-fits-all design so you can extract it directly into the installation path for "The Sims 3," automatically inserting the file into the correct folder; although your installation path may vary, the game's folder hierarchy does not.
Load "The Sims 3." If the mods were extracted to the correct place, you'll see a new dialog box appear when starting the game, listing "WooHooer" as an active mod. If you already have an existing family ready for this, load the save now. Otherwise, feel free to start creating the family.
Unpause the game once so the mod officially activates, indicated by a toast box in the upper right-hand corner. If you have free will enabled and don't want the Sims roaming around free while you figure out the rest, pause the game again.
Shift-click the currently selected Sim or the mailbox. Select "NRaas / WooHooer" to open a menu of options exclusive to the mod. Two categories are important for this task: Romance and WooHoo.
Select "Romance" followed by "Species." Enable "Allow Near Relation Romance" to remove the usual family restrictions for romantic interests. If you like to play with free will, this also reveals the option "Allow Autonomous Near Relation Romance." Return to the main mod menu; everything is saved automatically.
Select "WooHoo" followed by "Species" to allow the same interactions unrelated Sims normally get. Like the other category, you can enable "Allow Near Relation WooHoo" and "Allow Autonomous Near Relation WooHoo" at your discretion. Exit the menu and unpause the game to complete the changes, which will be listed in the upper right corner.
Although the mod should work immediately when loading the game, you might need to delete some cache files in your "Sims 3" folder. In "Documents\Electronic Arts\The Sims 3," delete the following .package files: CASPartCache, compositorCache, scriptCache, simCompositorCache and socialCache.
You must update your game to the minimum patch indicated by the version of the mod you download. If you cannot update your game for any reason, you'll need an earlier version of the mod that supports the patch version you have. You can see the patch at the bottom of the launcher when loaded.