Fanon:Cynthia Mars

Cynthia Mars (previously King; née Day) is the daughter of Wesley and Gretel Day, and the older sister of Alex Day. She went onto marry Arthur King, but had an affair with his brother Clayton King, which resulted in the birth of their daughter Selene King and Arthur divorcing Cynthia. She moved on to Lance Mars, and they had a son together named Drake Mars. Cynthia later married Lance, but on their wedding day she tragically drowned in their swimming pool.

Life leading up to The Sims 3
Cynthia and her family move to Sunset Valley. Through her mother Gretel, she is a witch, yet unexperienced.

Life leading up to The Sims 4
In The Sims 4, Cynthia lived in Magnolia Promenade. At first, she lived with her sister Alex, newly-wedded husband Arthur King, his brother Clayton, and three roommates (Clayton's friends) named Ehren Weston, Eric Di Marco, and Lance Mars. Cynthia ended up embarking on a love-affair with Clayton, her husband's brother. They would keep it low until Ehren witnessed them kissing, and she bribed him with money to move out with Eric (his now-boyfriend) and keep quiet, and so he did with Eric. Cynthia later fell pregnant with Clayton's baby and tried to pass it off as Arthur's, giving birth to a daughter named Selene. However, Arthur soon discovered the truth when he saw Clayton and Cynthia kissing at Ehren and Eric's wedding. Angered, he slept with Cynthia's sister Alex and divorced Cynthia. Cynthia and Clayton would break apart too, and Arthur would start a relationship with Alex, only to end it after a short period of time and move out.

Cynthia had eyes on Lance Mars and they were attracted to each other, leading to an intense committed relationship. Cynthia promised she'd never cheat again, and so she never would again. Clayton and Alex also got together, and so Cynthia was happy for them. Lance later impregnated Cynthia and he proposed to her during her pregnancy. They had a son together, Drake Mars. Shortly after his birth, Lance and Cynthia married at their home, but it would last for a short. Selene ended up almost drowning in their swimming pool in their backyard, and Cynthia dived in to save her—which she did, but she ended up getting tangled in her wedding dress and tragically drowned in the midst of it, witnessed by Selene, Ehren Weston and friend Carmen Bartholomew. After her death, Cynthia was laid to rest in the grounds of her home.