An affair happens when a Sim who is already in a relationship falls in love with another Sim or interacts romantically with a different Sim.

Getting caught

Having an affair can be risky, as getting caught can possibly ruin the relationship with the other Sim.

Ways a Sim can get caught

• WooHooing as another lover passes by on the same lot, even if they're on opposite sides of the lot. However, in The Sims 2, a Sim doing this will not be caught if the other lover is sleeping.
• Going on a date anywhere on the same lot where the other partner is present (if you ask someone on a date by calling them and go to a community lot it won't be found out, unless the partner walks by that lot). Being caught by another lover on a date will fulfil the fear of being caught two-timing.
• A lover views the flowers (reads a note on them) a date may have left. However, relationship drop won't be as large.
• A child who sees the adulterers mid-WooHoo may cry and attract the attention of the cheater's spouse.
• Sleeping in the same bed^[1] when the lover is around.
• Doing any romantic interactions^[2] with another Sim while the main romance is near the cheating couple.
• Hearing gossip from another Sim (this is not possible anymore in a patched game, but it was showcased in beta videos).

When this occurs, the Sim will be slapped^{[TS][TSC][TS2][TU:SITC][TSS]} and many relationship points will be lost.

Interestingly, Sims can be caught cheating by the ghost of a deceased Sim with whom they had a romantic relationship before that Sim died. The ghosts can even become furious with the Sim who cheated on them.

Getting caught by children

If children catch their parents cheating, they get the same relationship decreases with both their parent and the paramour and, if left to their own devices, may even attack their own parent or who the parent is having an affair with. They don't get any visible memories from this aside from any meetings, but effectively act like a Sim who has been cheated on. They'll either cry or get angry at the parent. However, if one of their parents had died and they somehow didn't know about it, it could cause needless drama if they consider looking for love again as cheating.

Jealousy

Whenever a Sim, who has a crush on or is in love with another Sim watches the latter partake in some romantic interaction with another, jealousy occurs. In The Sims 2, if Nightlife or later is installed, jealousy also triggers fury. This doesn't take into account whether or not the feelings are one-sided, which may be messy for unrequited crushes. If Nightlife or later is installed, and a Sim catches another Sim flirting with their partner, they will also be furious at their partner, regardless if their partner rejects the flirt.

The witnessing Sim often loses the crush or love marker, and his or her relationship with the cheater and the one he or she is cheating with plummets into the negative. If he or she doesn't know the other person, a "Met Sim" memory is added along with the affair and possible "Fell Out of Love" memories.^[TS2] This relationship drop enables breaking up, assuming the Sims were going steady, engaged, or married.

The cheated-on Sim may reject the cheater should they try to interact with them romantically.

In The Sims 4 after Patch 162, players are able to manage a Sim's romantic boundaries in Create a Sim. The options allow the player to change what interactions witnessing their partner's doing will cause jealous from non-physical romance, physical romance, woohoo, and if they're willing to be talked about changing their boundaries.

Repairing relationships

Getting caught in an affair won't always spell the end of a relationship, but it can make bringing it back up extremely hard, especially if the scorned Sim is more interested in fighting with the other one (this could cause the other to lose their own crush/love markers, and even trigger fury to make things that much harder).

To apologize for an affair, select the cheater and click on the spouse cheated on and select "Appreciation/Apologize" from the pie menu, but only after the fury^[TS2:NL] or "Betrayed" moodlet^[TS3] has ended; if not, the betrayed Sim will not accept the apology. It is easier to repair relationships if the Sims are BFF's, if the Sim uses the "Smooth Talk" interaction,^[TS2:FT], "Repair relationship with..." interaction after studying "Couples Counseling"^[TS2:AL] or use the Cupid's Corner section on the phone to "Go to Cupid's Counselling with..."^[TS4:L]

In The Sims 4: Lovestruck, Sims are able to go on a repair date that is specifically only available to Sims in a low or negative romantic relationship.

If a couple somehow manages to get tarnished by an accidental affair, it may be best to use cheats or hacks, such as InSimenator, to fix the problem, or exit without saving.

As well as repairing jealousy, there is also a way to prevent it. In The Sims 3: World Adventures, a new lifetime reward is added; No Jealousy. This reward costs 10,000 lifetime happiness points. Purchasing the lifetime reward eliminates jealousy altogether. The No Jealousy reward also makes it possible to create a polyamorist Sim, with multiple lovers living under one roof.

Effects of affairs

The Sims, The Sims Bustin' Out and The Urbz: Sims in the City

When cheating occurs, the Sim will be slapped and the two Sims will lose -50 relationship points. The Sim who gets cheated on will have their social need depleted.

The Sims 2 and The Sims Stories

As in The Sims and The Urbz, the Sim will be slapped and relationship points will be lost. In Nightlife, Deluxe, Double Deluxe and The Sims Stories, this can also trigger Fury.

The Sims 3 and The Sims Medieval

When affairs/cheating occurs, the Sim will be jealous and some relationship is lost. No points are lost if the No Jealousy is chosen.

With The Sims 3: Generations, when cheating occurs romantic reputation may change, and after sometime the spouse/lover may get the "Betrayed" moodlet and will autonomously accuse the Sim of being a cheater and their relationship will decline.

The Sims 4

If an affair/cheating is noticed by the betrayed lover, they will become angry and relationships points will be lost.

Sims involved in an affair can be convinced to leave their spouse, which immediately divorces the Sim from their spouse. The Sim that was cheated on will not get the divorced moodlet. The spouse that was cheated on will automatically become upset (if the cheating spouse is seen having an affair) and will cry.

With The Sims 4: Lovestruck, when cheating occurs their romantic satisfaction can plummet as well as enter a heartbreak mode where in if they're repeatedly heartbroken from boundaries being broken can potentially die of heartbreak.

How affairs/cheating occurs

The Sims

• Using a romantic social such as "Kiss" when that Sim has a lover. A sound will also be played if cheating occurs.^{[TS][TSC][TSBO]}
• Using an Act Romantic social or the Blastikiss Power Social.^[TU:SITC]
• Giving a hug, even if it isn't romantic, to another Sim while a lover is in the room.^[TS]
• Dancing with or complimenting another Sim while a lover is in the room.^[TS]

The Sims 2 and The Sims Stories

• Using a romantic social such as "Kiss" when the Sim is married or has a lover.

The Sims 3 and The Sims Medieval

• Using any romantic social on another Sim if they have a lover or husband/wife. No Jealously LTR prevents this effect.

The Sims 4

• Using any type of romantic social on another Sim if their lover is in the same room or are close by.
• With editing the romantic boundaries, cheating and affairs can only occur through non-physical romance, physical romance, and/or woohoo

References