Alternate universe

The Sims 4 exists in an "alternate universe," separate from the timeline established in The Sims, The Sims 2, and The Sims 3. The alternate universe was created to allow the developers of The Sims 4 more creative control over the Sims and families that appear in the game. It allows well-known and established Sims and families from previous games to appear without disrupting the continuity set by the first three games. Thus, events and Sims which exist in the "backstory" of The Sims 4 can, but do not necessarily, exist within the continuity of the first three games, and vice versa. It could give players a chance to create their own storyline in their own game without the worry of altering the creator's timeline. It is known that Sunset Valley generally took place before The Sims 2, so some Sims would've been dead by the time The Sims 2 started. The Sims 4 alternate universe gave a chance to continue the player's favored Sims' storyline.

Examples of differences between continuities

 * In The Sims 2, it is established that Nighat Caliente is the deceased mother of twins Dina and Nina Caliente. The Sims 4 establishes that Katrina Caliente is the mother of the twins. Additionally, unlike Nighat, Katrina is alive at the start of the game.
 * In The Sims 3, Mortimer Goth and Malcolm Landgraab are children, but in The Sims 4, Mortimer is an adult with children of his own and Malcolm is only a teen. Similarly, Don Lothario and Cassandra Goth are both adults about to marry in The Sims 2, while Don is a young adult and Cassandra a teen in 4.
 * In The Sims and The Sims 3, Mortimer and Bella Goth are the same age, while in 4 Mortimer is an adult, while Bella is at the start of her young adult life stage. As well, Cassandra and Alexander are far closer in age in 4's continuity, with Alexander remaining a child while Cassandra is aged down to a teen.
 * The Malcolm Landgraab from The Sims 3 has the good trait whereas the Malcolm Landgraab from The Sims 4 has the evil trait in its place.
 * Dirk Dreamer, Dustin Broke, and Holly Alto all appear in The Sims 4: Get Famous, but with different appearances and personalities. Dirk and Dustin still retain some similarities with their The Sims 2  counterparts, but still have some major differences, while Holly Alto looks completely different from her The Sims 3  counterpart.