If you are looking for a thriller/espionage series with characters that become part of the family over time, you might check out Daniel Silva's Gabriel Allon novels, beginning with The Kill Artist. This is the ninth volume in the series. Allon's nemesis is an especially brutal one, and Allon is provoked to match that brutality to prevent awful things from happening. If you're an Audible subscriber, or think you'd like to be one, Phil Gigante does a first-rate job adding voices to Silva's characters. I especially like Mr. Gigante's version of Ari Shamron, the legendary Israeli agent who is Allon's father-figure, mentor, and friend.