Isaac Santiago is the second child of Penelope and Zane Santiago, as well as the second grandchild of the late Justine and Joseph Fenderson, and Julian Santiago. He is the older twin of Lindy, the younger brother of Kendra and the older brother of Aiden and Tanner. He is also the Uncle of Jamie Tanner.
Isaac is an ex-college student. Like his sister Kendra, he is a Nerd, but has a higher interest in comic books than gaming.
Isaac was born to Penelope and Zane Santiago in Part 5, before his twin sister Lindy, and got the Clumsy and Loves the Heat traits, as well as the Nerd hidden trait. Isaac aged up into a Toddler in Part 7, before Lindy. He aged up into a child on his own in Part 13, once again, before Lindy. Due to his modest early development he gained the Brave trait. As a Toddler, Isaac did not have a good relationship with his dad, which they try to fix once he ages up.
Isaac aged up into a Teen between Parts 17 and 18 and gained the Ambitious trait. He is seen spending more time with Zane. Lifesimmer said she wanted Isaac to be a bookworm and a comic book geek; like Lindy, he appears disinterested in dating. In Part 20 Kendra signed him up for the newspaper club. Isaac attended the dance without a date in Part 21 where was voted prom king and started hitting it off with a girl named Nora Lamar, although he was twice rejected by his existing crush. He also got in a fight with a nerdy classmate. Lifesimmer stated that she would consider making Isaac gay, despite him being romantically involved with a girl, meaning that Isaac could be bisexual.
Isaac and Lindy went to college together as Young Adults, where Isaac seemed more interested in anything other than his studies. In Part 41 Issac seemed to take a liking to Lindy's friend, Ashley, which is made evident when he stares at her bikini-clad chest. Ashley, on the other hand, appears not to be interested in him.
Isaac went on to attend the Lucky Palms Community College where he studied Business for the Criminal Career.
Isaac appears alongside his parents and siblings, sans Kendra. He has left community college due to the mod becoming obsolete and is currently pursuing his career.
- Isaac went through a bald phase in which he would often sport a toupee.
- Isaac shares his favorite color with his twin sister.
The Fenderson-Santiago Family By appearance:
Justine Fenderson (nee Smith) - Joseph Fenderson - Luna Fenderson - Penelope Santiago (nee Fenderson) - Jai Fenderson - Tori Fenderson (nee Dunbar) - Ava Fenderson - Zane Santiago - Julian Santiago - Kendra Tanner (nee Santiago) - Isaac Santiago - Lindy Santiago - Karie Dunbar - Aiden Santiago - Davina Dunbar - Tanner Santiago