Sim can propose to another Sim, depending on their relationship. If the other Sim accepts, the two Sims will get married.
In The Sims, any two opposite-sex adults can get married. Either Sim can propose, but the proposer must be at home to do it. Whether the other Sim accepts or not depends on their mood or the relationship between the two Sims. If the other Sim accepts, however, both Sims will change into their formal clothes and share what's either a dance or a polite kiss, and the proposing Sim will be charged §1000. Sims who don't have §1000 can still marry; they'll be charged half of whatever funds they have. The Sim who was proposed to will take on the family name of the other Sim and move in with them.
Since there are no defined family ties or family relationships in The Sims, the option to get married is not available to Sims who already live together. Players can stage marriage ceremonies between Sims who live together, but the "Propose... Marriage" interaction won't be available because they're already considered part of the same family.
Couples can ask one another to "Move In" if they do not already live together. Whether the other Sim accepts depends on their mood, their relationship, and the quality of the other Sim's house. The Sim who moves in will take on the family name of the Sim who proposed, even if the two are simply good friends. (This is unavoidable, as Sims in The Sims do not, properly speaking, have surnames.)
Marriage in The Sims is an event, not a condition. So, while Sims cannot get a divorce, a Sim who has married into one family can marry out of it and into another family. If the partner of the Sim who is changing households has a relationship with the proposer, that relationship will drop. Also, if the relationship between two Sims in a family is low enough, they can choose the Attack option and fight each other. Which Sim wins depends on their Body skill. The Sim who loses may choose to move out, and if they do, they will never be seen in the game again.
When two Sims are in love, they can get first engaged and then marry (with or without a wedding party). If the Sim to be married is not living with his or her partner yet, they will move in as soon as the wedding ceremony is over. Either Sim can propose.
The Sim who initiates the "Get Married" interaction is the Sim whose last name both parties to the marriage will take. However, a program such as SimPE can edit this.
There are two ways in which Sims can get married. Engaged Sims can get married with the "Get Married" interaction, in which the two Sims exchange vows and kiss to signify their marriage. It is also possible for two Sims to get married under a wedding arch without throwing a wedding party. Unlike the simple "Propose... Get Married" interaction, under a wedding arch, there will be a short scene of the Sims exchanging rings, with any other Sims clapping in the background. The Sim who initiates the marriage proposal is the one whose last name they will take.
The other (and more "traditional") way to get married is to have a wedding party. This is basically like a normal party, only the Sims are expected to get married. The wedding arch may or may not be used. The difference between normal parties and wedding parties is that every guest will be in their formal clothes, and any guest invited will show up even if they have a low relationship with that Sim.
Marriages between two Sims of the same sex are referred to as "Joined Union" in The Sims 2, although a Wedding Party is still called a wedding party.
Like a regular wedding, when two Sims of the same gender are in love, they can get first engaged and then enter a union (with or without a wedding party). If the Sim to be joined is not living with his or her partner yet they will move in as soon as the wedding ceremony is over. Again, the Sim who initiates the interaction is the one whose last name both parties to the union will take.
Joined unions provide fewer aspiration points than marriage. However, a hack available at www.simbology.com allows same-sex partners to enter marriages with the same titles, wants and fears as with opposite-sex partners: Same Sex Mods
Being left at the altarEdit
There is a chance that a Sim getting married could get "left at the altar", even though Sim weddings do not involve altars. When this happens, one Sim will hesitate while the marriage is taking place, and then run away, leaving the other Sim behind. This could happen if one of the Sims is having an affair or has a fear of marrying their partner. It might also happen if the two Sims don't have a strong enough relationship, or if the Sim being proposed to has low needs (and thus in a bad mood).
When a Sim is left at the altar during a wedding party, those who attend will have a lowered relationship with the Sim that left the other at the altar. The closer the attendees are to the Sim who was left at the altar, the more they will dislike the other Sim.
Sims who are in an exclusive relationship can propose marriage to their other half and become engaged.
The Sims 3: Generations provides extensive new features when it comes to proposals and marriage. Before proposing, the player has the option to let their Sim ask one parent for permission to marry their child. The engaged Sims can have the opportunity to throw a bachelor(ette) party, where a skimpy-outfitted dancer shows up to dance. Children are not allowed to be invited to the party but children who live in the household where the party will take place may stay. They can then either have a "Private Wedding" by marrying on the spot or a wedding party, which can either be done at home or on a community lot. Other features in marriage include wedding arches, where Sims can opt to get married under, and wedding cakes, which is a lot similar to the birthday cake except the newlywed couple cuts the cake together instead of blowing candles.
When Sims wed, the last name taken by the couple will be that of the Sim who proposed. Single parents who marry under the criterion that his/her spouse was the one who proposed, they, along with all their children who are not adults(including the ones not in the household), will take on their new step-parent's name. (E.G. A single mother marries another man, hence her children will receive their step-father's name.) The same rule applies to newlyweds who had children together before marrying; they originally take their mother's name and their future last name depends on whomever proposes. It's important to note that a Sim's last name can be changed via an interaction performed by the Sim in question at the City Hall.
If the player wishes for a Sim couple to get married, the player first must build up their relationship until they are in love, and have a romantic interest. Then after they have a full relationship bar, the action "Propose Going Steady", under the romantic section, will become available. Sims will then become boyfriend and girlfriend. Eventually, they can opt to marry.
When a couple (whatever gender combination it may be) consisting of two Sims who have their separate offspring that are in a romantic relationship with the other, after marrying, their children still see each other as Boyfriend/Girlfriend, but cannot perform romantic acts on one another as they are now step-siblings. They can only perform romantic acts when their parent/step-parent dies or their parents divorce. Though if a couple are already married when their parents marry each other, they can perform all romantic interactions.
Also note that in The Sims 3, unlike in The Sims 2, there's no distinction between same and opposite-sex marriages. The amount of Lifetime Happiness is the same for both kinds of couples when they go steady, get engaged and finally get married. Further, in the family tree of same-sex couples it shows their spouse as either their husband or wife, the same as it does for opposite-sex couples.
Throwing a wedding party Edit
In The Sims 2 and The Sims 3 a wedding party can be held by selecting "Throw Wedding Party" on the phone. This is basically like a normal party, only the Sims are expected to get married. The wedding arch [TS2][TS3G] may or may not be used.
There is limited number of Sims who can be invited to a wedding party. In The Sims 2, players don't need to invite the bride or the groom to the party if they don't live together, because they will automatically come by themselves. Invited Sims will arrive with Formal wear. When the marriage takes place, both Sims switch into wedding attire (Formal wear) and head beneath the wedding arch.[TS2] Guests will gather around, and the Sims exchange vows and kiss to signify their marriage.
A wedding party is scored like a normal party. How well it scores depends on how much the guests are enjoying the party. If players can keep all the guests happy until the end of the party, it will become a great wedding party, and the married Sims will get a good memory about it.[TS2] Otherwise, players can have a horrible wedding party if the guests are not enjoying it. It's better to set up party objects to keep guests happy, such as a stereo, buffet table, bar, etc.
If the wedding party is successful, a limo will come for the newlyweds to take them on their honeymoon. While they are on their honeymoon, their need bars will have a significant increase. If Bon Voyage is installed, the player can arrange for the Sims to have an actual honeymoon trip.
Interestingly, in The Sims 2, if the wedding party takes place with many family members around, and there is music playing, the bride may experience a want to dance with her father after the ceremony and the "first dance" with her husband.
If two married Sims have their relationship with each other fall enough, such as through witnessing an affair, one Sim can kick the other to the curb. To have the couple get a divorce, choose whichever Sim will do the breaking up, click the other spouse, and select "Break Up". This option will only appear if the active Sim's relationship is low enough with their spouse; however, this option is always available in The Sims 3. The divorcee will then flee the lot and reappear in the Family bin in the neighborhood screen. They do not have the option of have taking any children they had or of remaining in the house. If the player wants them to stay in the house after the divorce, they will have to be moved back in.
In The Sims 3, the player will never see the word 'Divorce' in the game unless it is a wish during a Mid-Life Crisis, or a memory if The Sims 3: Generations is installed. However, the "Break Up" option will almost always be available. When the "divorcer" divorces the "divorcee", they will still live together, however either Sim may have a wish to move out. Their relationship may drop into the red zone, depending on how good their relationship is the moment they break up (a full relationship after the divorce will still make the relationship be in the green zone), however the divorcee will experience more emotional turmoil, and will receive a large Lifetime Happiness drop as well as a moodlet for being betrayed/broken up with. This moodlet will last for days. If the divorced couple has children, the divorce will affect them badly too. If the player wishes to avoid this, it is best if the divorcer is a normal Sim while the divorcee is someone with the "Commitment Issues" trait so that there will be no hard feelings for either, except when it comes to the children.
In The Sims 3: Late Night, if the married Sims have relatively high celebrity status, if the rumors begin to float about the divorce, it can be considered a public disgrace, but not many would react negatively to it.
In The Sims 3: Generations, if a Sim catches their spouse cheating (doing anything under the Romantic category with another Sim), their relationship will go down and it will take at least five days for the Sim to make the negative moodlet disappear. If the cheating is constant, the Sim can sometimes involuntarily (as the player cannot cancel the action) divorce the cheater on the spot.
In The Sims 4, there is a "divorce" option under the "mean" option for a married Sim to his / her spouse, instead of the "break up" option.
To avoid divorce, it's necessary to wait for their fury with each other to subside or, in The Sims 2: Apartment Life, have them perform the interaction called "Repair Relationship With..." which will have the two Sims attempt to deal with their marital problems. In The Sims 3, if one's charisma is high enough, the sim can use the smooth recovery interaction to try to repair the relationship.