This child is either the second son or daughter of Missy Cooper and her first ex-husband. It's revealed in the season 11 finale, "The Bow Tie Asymmetry", that Missy's pregnant with her second child. The child wasn't born yet and it was unplanned. Missy was pregnant when she and her first husband split up. The child and the son went to live with his father and got sole custody.

Characters Main Leonard Hofstadter  ‧  Sheldon Cooper  ‧  Penny Hofstadter  ‧  Howard Wolowitz  ‧  Rajesh Koothrappali  ‧  Amy Farrah Fowler  ‧  Bernadette Rostenkowski-Wolowitz  ‧  Stuart Bloom  ‧ The Social Group  ‧ Emily Sweeney  ‧  Leslie Winkle
Recurring and Minor Debbie Wolowitz  ‧  Barry Kripke  ‧  Priya Koothrappali  ‧  Dr. V. M. Koothrappali  ‧  Mrs. Koothrappali  ‧  Stephanie Barnett  ‧  Lucy  ‧  Mary Cooper  ‧  Zack Johnson  ‧  Beverly Hofstadter  ‧  Mike Rostenkowski  ‧  Alex Jensen  ‧  Professor Proton  ‧  Missy Cooper  ‧  Ramona Nowitzki  ‧  Dan  ‧  Josh Wolowitz  ‧  Dennis Kim  ‧  Althea Davis  ‧  Jeanie  ‧  Cinnamon  ‧  Mrs. Rostenkowski  ‧  Wyatt  ‧  Claire  ‧  Kurt  ‧  Eric Gablehauser  ‧  Dave Gibbs  ‧  Dimitri  ‧  Alfred Hofstadter   ‧  Meemaw  ‧  Jimmy Speckerman  ‧  Susan  ‧  Randall  ‧  Bert Kibbler  ‧  President Siebert  ‧  Janine Davis  ‧  Richard Williams  ‧  Halley Wolowitz  ‧  Neil Michael Wolowitz  ‧  Denise  ‧  George Cooper Jr.   ‧  Larry Fowler  ‧  Anu  ‧  George Cooper Sr.  ‧  Marissa