Not Sure If We’ve Spiraled About This Yet…

But ummmm where is or what happened to THE THIRD JACOBS SIBLING?! For two seasons now, the kid has been in photos! Did he die?! Is that what triggered both Cal and Nate’s anger issues? Is he at boarding school? Is he emancipated (not to be confused with Mimi aka Mariah Carey)? Please share your best theories because I need ANSWERSSSSSS!