JJ discovers that she is pregnant in the episode The Crossing with her partner Will's child. This pregnancy eventually leads to her temporarily leaving the BAU on a maternity leave during the following season.
Henry was born during Memoriam, and after the team gets to meet him after finishing a case, JJ asks Reid and Garcia to be Henry's godfather and godmother, respectively. In Normal, JJ brings Henry to the BAU headquarters after the team solves a case, and the team takes turns holding him.
In Amplification, after a homegrown terrorist lethally poisons dozens of Annapolis parkgoers with a modified version of anthrax, JJ becomes concerned after learning that a seven-month-old baby was poisoned with anthrax during the Amerithrax attacks and calls Will to tell him to keep himself and Henry safe. The call isn't answered, and this worries JJ further. When the case is concluded, JJ most likely lets go of this fear.
Henry is seen with his parents in a pharmacy in 100 while they're waiting for a prescription to be filled. It is this visit that actually helps bring the team one step closer to concluding the current case.
Henry suffered from a seizure and had at least one hospital visit prior to There's No Place Like Home. He then consequently contracts a fever that becomes worse, culminating in another hospital visit escorted by Will. This forces JJ to return home, but due to the severe weather conditions, she still has to stay in Kansas. After the case is concluded, JJ calls Henry and tells him a bedtime story.
His role is greatly expanded in the season finale episodes Hit and Run. In the latter episode, Henry is taken hostage by psychopathic serial killer Izzy Rogers, unbeknownst to him, as leverage for Will to assist her and her boyfriend in committing a terrorist attack. He asks her to play a game of hide-and-seek, to which she attempts to scare him by singing "Ring Around the Rosie" in an eerie tone, then telling him a story about her (presumed) grandfather, who allegedly resembles him and shares the same name, but both ploys fail. When Izzy is later distracted, Henry hides in a closet, hoping to play hide-and-seek with her. Izzy then gets into a struggle with JJ, who emerges victorious. By the end of the episode, he witnesses Will propose to JJ with Rossi and attends the wedding, becoming amazed by a magic trick performed to him by Reid.
In The Good Earth, Henry doesn't want to go trick-or-treating because he overheard his parents talking about monsters. JJ helps him get over his fear by challenging Henry to identify who are real monsters and who are not. By the end of the episode, Henry dresses up as his favorite profiler, his godfather Reid. He briefly reappears in The Apprenticeship, attending a bureau softball match with JJ.
In Nanny Dearest, Henry receives a bath from JJ, just before she leaves to investigate a case. Before she leaves, she promises him that she will be back as soon as she can. By the end of the episode, JJ returns home to find Henry already sleeping. As Will approaches her, JJ closes the door to his bedroom, taking one last loving look at him.
Henry briefly reappears in 200, when Will hands him over to CSU Tech Agent Gina Sharp, who takes care of him as the BAU search for JJ, who has gone missing. In that same episode, it is revealed that, in 2011, he was about to have a sibling, but due to an explosion that Tivon Askari intentionally set off, his mother had a miscarriage and the unborn baby died.
In If the Shoe Fits, Henry learns about his deceased aunt Rosaline from his grandmother Sandy. He later asks JJ about Rosaline, which enrages her, since she and Will were planning to tell him about Rosaline's suicide when he is much older. This leads to a fight between her and Sandy about keeping Henry in the dark over the subject. By the end of the episode, however, JJ comes to terms with the tragedy and tells him about the happier times she spent with Rosaline.
In The Storm, it is shown that he had befriended Hotch's son Jack, with whom he carpools and shares comic books. Both children, along with JJ, witness Hotch being arrested by a SWAT team for conspiracy. He and the rest of the family later occupy the BAU offices as the team struggles to clear Hotch's name and solve the case. By the end of the episode, Henry attends a party hosted by Rossi.
- Mekhai Andersen, the child actor who portrays Henry in 100 and onward, is actually the real-life son of A.J. Cook, the actress who plays JJ.
- Henry's birthday was confirmed to be October 28, 2008 (Memoriam).
- In 200, however, Rossi mistakenly states his birthday as being November 12 while attempting to figure out the four-digit combination code for a briefcase that was found hidden in JJ's office. This was most likely the writer's attempt at referencing the original air-date of Memoriam, the episode in which Henry was born: November 12, 2008.
- When JJ goes back to work after her maternity leave, she was shown wearing a new ring with citrine numerous times since. She once said both Will and her got one because it was Henry's birthstone. Citrine is November's birthstone.
- He seems to enjoy playing soccer with his mother (Hit).
- His favorite profiler (presumably besides his own mother) is his godfather Spencer Reid (The Good Earth).
- He likes Spider-Man (Boxed In).
- He is good friends with Jack Hotchner, with both of them sharing a liking of comic books (The Storm).