Lilith resides in the Pleasant house in Pleasantview with her parents, Daniel Pleasant and Mary-Sue Pleasant, and twin sister Angela Pleasant. She and Lucy Burb are cousins. According to Lilith's memories, she and Dirk Dreamer were childhood friends, and are now dating. Their parents' memories indicate that she is the younger of the Pleasant twins, though that is not explicitly stated. When first playing the family, the twins are both 10 days away from becoming adults.
Lilith is also the granddaughter of Jeff Pleasant and Diane Pleasant (her father's parents), and Herb Oldie and Coral Oldie (her mother's adoptive parents). Jeff and Diane passed away when Lilith was a toddler, though she has no memory of their deaths.
She and her twin are, or at least appear to be, complete opposites, emphasized in their choice in clothes and room decoration. While Angela dresses in a light green sundress, Lilith wears a black gothic dress with black boots, and has black spike collars on her neck and wrists. Lilith's room is "dark," with a dark red carpet and stone walls, and no computer (or even desk); contrastingly, Angela's room is a bright shade of pink with a computer in her room. While it's not certain why Lilith's room is more sparsely decorated than Angela's, Lilith's things are generally pricier, costing between §140 and §1,200. However, it does appear that each twin was allowed to decorate her room as she chose.
Lilith's memories strongly suggest that, when they were young, her parents favored Angela over her, since, unlike her sister, she was never taught her toddler skills. No reason for this is given, but it likely contributed to her bad relationship with her parents and her sister. She considers herself to have been treated unfairly, and some players think Angela may be the reason, thus making her slightly hostile toward her sister.
Despite Lilith and Angela being polar opposites, the two share the Popularity aspiration and a very similar personality, though Angela is a little bit neater, nicer and more playful. Lilith's genetics are exactly like Angela's, with the exception of having thinner eyebrows.
Lilith starts out with no visible skills (though she may want to gain some) and poor grades, though the player still has time to raise her grades if they wish.
Lilith hasn't met Dirk's father, Darren, and vice-versa. The reason for this is unknown, but some players speculate that it could be so Lilith doesn't have a repeat of the trouble her sister's boyfriend is currently undergoing (Dustin and Daniel are enemies at the start of the game).
Her name may be a reference to Lilith, the queen of the dark. Seeing as the name Lilith is translated as Night Monster or Night Creature, it may be another reference, as Lilith is gothic and prefers dark things to the cute ones that her twin sister, Angela, likes.
An official Maxisrecreation of Lilith and her family was uploaded to the The Sims 4 Gallery on February 22, 2019, marking the 19th anniversary of The Sims. In this timeline, Lilith has a "C" grade instead of "D-" and is friends with Angela instead of rivals. She is also friends with both of her parents, suggesting that they didn't favor Angela over her growing up. Furthermore, she is not acquainted with Dirk Dreamer, and if they meet, they could not date until Lilith ages into a young adult. Both Angela and Lilith will turn into young adults in 12 days.
Lilith carries incomplete homework in her inventory and has no skills. She also has a tattoo of three black butterflies on her upper back, which is visible between her choker and shirt.