Alexander Goth is a pre-made Sim who is introduced in the Sims 2 game, in which he lives as the son of Bella Goth and Mortimer Goth, with his sister Cassandra Goth. He has pale skin and Harry Potter like glasses. Unlike the rest of his family, Alexander did not exist in The Sims and is a new addition to The Sims 2. He seems to share his father's intelligence despite his young age and is enrolled in private school. Due to the apparent age gap between both of his parents, it is believed that he was born just before Mortimer had turned into an elder, making a big age difference between him and his sister. But there is a picture in the family album of Alexander being held by Cassandra when he was a baby, so it's likely he was born a day or two before Mortimer aged.
There is a book in the Bachelor home, Alex's family, entitled Murder in Pleasantview. It is written by Alexander Goth, although it is unlikely that it is the same Alexander. There is a possibility that the title of the book is a hint for the players on a more realistic method regarding what the player should to do about Bella Goth's disappearance mystery if the players wish to connect their story as close to The Sims 2 as possible. Since there are no possible ways of alien abduction in The Sims 3 base game.