Family relationships are the bonds between family members. There are special interactions for individual family members beginning with The Sims 2.
The family relationships in The Sims are very simple. Two Sims are either members of the same family, or they aren't, and all Sims who live in the same house are considered part of the same family. Even when two Sims marry, what makes them part of the same family is that one moves in with the other. That the two Sims are married is not recorded.
The parent-child relationship does exist, but is not recorded as such. It only exists while the child remains a child. Using the "Age of Instant" charm[TS:MM] or a third-party program to turn a child into an adult will break the parent-child relationship.
Likewise, sibling relationships are not recorded as such. Children living in the same house are considered to be siblings, but if one or more of them is turned into an adult, that relationship will not persist.
Of course, players can define two adults as parent and child, or as siblings, and play them as such, but the game itself will not define any relationship between them.
The Sims 2
List of Family Relationships in The Sims 2:
Life-extending items such as the Elixir of Life and the Cowplant, or resurrection can allow a Sim to live long enough to be a great-grandparent. However, great-grandparents and great-grandchildren who are alive at the same time will not be shown as related in the relationship panel.
Children and younger Sims taken away by the social worker but later adopted by other households will still be known to their old households. However, any traces of their family relationships will be erased except for the memory that a family member was taken away (which makes them ineligible for adoption).
In The Sims 2, Sims have interactions that can only be performed with family members.
- Encourage: Using this interaction, a Sim can encourage a younger Sim's behavior and gradually change their personality. For example, if an older family member encourages niceness often enough, the younger will eventually be kinder to people.
- Family Kiss: Two blood-related or unrelated (somebody who has moved in to join the family but has no relations to any of the family members blood-wise (although they could be a pre-existing Sim's love interest)) family members can give each other a family kiss. If a child Sim kisses another family member they will wipe their own lips with their arm afterward. If a Sim has made their spouse furious at them (e.g. from cheating or arguing), the only kiss they can perform is family kiss (if any).
- Babies: If an infant Sim exists in the family, a related Sim can cuddle and play with them. If an unrelated Sim exists on the lot they cannot perform "cuddle" or "play with". They can only "change diaper", "let [sim name] out" and "get bottle for [sim name]".
The Sims 3
In The Sims 3, Sims do not have interactions that can only be performed with family members, with the exception of babies as in The Sims 2.
- In The Sims 3, family relationships always show up in the relationship bar, but a Sim's relationship with a family member depends solely on their interactions with said family member (no added instant bonus for being related, except when living together there is more time to talk with one another).
- Also Sims with the Family-Oriented trait do have an easier time teaching toddlers to walk, talk and potty training them. They also have the option to hug, praise and encourage to build skills more often than other Sims.
List of Family Relationships in The Sims 3:
- Aunt/Uncle (Relationships for Grand Aunt/Uncle don't show)
- Niece/Nephew (Relationships for Grand Niece/Nephew don't show)
- Cousin (first cousins only)
- Descendant (Into The Future expansion pack only) - not shown in the base game's family tree and list of descendants can change depending on what is happening to a Sim's 'present' life
The Sims 4
Relationships in The Sims 4 function similarly to those in The Sims 3. The Genealogy tree wasn't present in the base game, but was re-added in Patch 12.
- List of family relations in The Sims 4
- Aunt/Uncle (the siblings-in-law of a Sim's parents are not counted)
- Cousin (first cousins only)
- This section is in need of additional information. You can help The Sims Wiki by expanding this section.
Conflicts in family titles
At times, Sims who do not stay loyal to their spouse or commit somewhat incestuous acts by marrying relatives often create conflicts when it comes to labeling family relationships. Below are some of the examples:
- If a man has kids with two women who happen to be sisters, his two children will be both half-siblings and first cousins. In real life, aforementioned children in this situation would be labeled "three-quarter siblings", but that kind of serious coding would be too deep and potentially affect other things.
- Because The Sims 3 only recognizes the first cousins (the children of a Sim's parent's sibling) and is only considered an aunt/uncle if he/she is the brother/sister of the Sim's parent, it is therefore possible for a Sim to marry their parents' first cousins. The Sim's parent will originally see their cousin as "Cousin" but will see them as "Daughter/Son-In-Law", regardless of their age.
- Excessively adulterous Sims can have as many children as they want. Because they are only related through one parent, half-siblings can marry their half-siblings' other parent. This will consider them as both half-sibling and step-parent. A step-child is only labeled as one if one of his/her parents marries another spouse. Therefore, if his/her biological parent dies, he/she can opt to marry their former-step parent and have children with him/her. If they have children, their child will be the half-sibling/nephew/niece of any child the former-step parent and his/her former spouse have.
- Uncommitted male and female Sims have a child but the female Sim has another child with the male Sim's son and subsequently marries him. The male's Sim son is the half-brother/step-father of the first child while the second child is the half-sibling/niece/nephew of the first child.
- If two female Sims marry each other's fathers, they will be recognized as each other's step-mother, and the husbands as father-in-law to each other. Likewise, their children recognize each other as their aunt/uncle, although they recognize each other as niece/nephew in The Sims 4.