What is the name of Charles Boyle's adopted son?

Charles Boyle's adopted son is Nikolaj. Charles and Genevieve Mirren-Carter adopt him after meeting him in the fourth season, expanding Charles's already intense family life into parenthood.

Nikolaj is a young boy from Latvia, and Charles is immediately enthusiastic about being his father. His name is pronounced in a way that becomes a recurring joke: Charles insists on the correct pronunciation while Jake repeatedly mangles it. Nikolaj later appears in several family and precinct storylines, including moments involving Charles's parenting style.

A common mix-up is confusing Nikolaj with Charles's other relatives or with Genevieve, Charles's partner. Nikolaj is not Charles's biological son; he is his adopted child. The character is also played by actor Antonio Raul Corbo, who appeared in multiple Brooklyn Nine-Nine episodes. The adoption adds another layer to Charles's relationship with Jake, who becomes Nikolaj's godfather.