Finn Brady is Cheryl Masters's long lost son, Gemma Masters's half-brother and John Constantine's apparent nephew
from Ireland. First appearing in Hellblazer issue 293, it was found out that Cheryl once got pregnant as a teen, after which her father Thomas forced her to leave the baby in a hospital. The baby soon ended up in the care of a nurse named Eva Brady, who named him Finn.
Unlike others in the Constantine family, Finn grew up a normal life as a well-known doctor and small philathrophist. He was married to woman named Sia and they had three children (two boys and one girl). During the "Curse of the Constantine" storyline Finn began to be enamored in magic, and he himself was framed as a serial killer, who had been killing a number of people in Ireland. The serial killer turned out to be his foster brother, Declan Brady, who was also a mage and a big fan of John Constantine. He and John finally crossed paths when John promised his sister to find him in order to free her soul from Hell. Both of the fights off the real serial killer and Cheryl's soul was finally freed.
Finn was also present during John Constantine's funeral, where he showed that he had gotten interested in magic and that his relationship with Sia has started to fall apart.. He once saved Epiphany when she was attacked by a disguised Julian, and the two started a relationship of which John (who at that time they thought was dead) approved.