It took a lot to get Jack to the Seattle Fire Department in the first place after his spotty childhood. In Season 5, we learned a bit more about what happened to him when he was younger. Basically, his biological parents had him when they were still in high school, so they put him up for adoption. However, Jack was never adopted. He spent his entire childhood and teenage years in unstable foster care.

In fact, he was almost adopted in 2002 to a family with two siblings. However, the house caught on fire, which killed his almost-parents and separated him from those he thought of as a brother and sister. After the incident, Jack was thrown back into the foster care system, and didn’t really find a family until he became a firefighter and found his Station 19 family.

By the end of Season 5, we learn even more about Jack’s past. Jack learns about his biological parents and finds out that he actually has a biological brother. However, his parents kept his brother, so Jack has to deal with many confusing emotions regarding this newfound knowledge. This also leads Jack down a path of uncovering incidents of child abuse in his past, so it’s safe to say that he had plenty of demons heading into Season 6.