Get Ready to Aww: Here's What Donnie Wahlberg Calls Tom Selleck Off-Camera

Since 2010, Blue Bloods viewers have been following the lives of the Reagan family dynasty as they tackle cases and battle politics while maintaining their tight-knit bond as a family.

With Season 13 currently airing, the show has stood the test of time and shows no signs of stopping anytime soon thanks to the dedication of its fans.

The immense popularity of Blue Bloods is a testament to its great writing and impressive ensemble cast, which made a lasting impression on viewers by demonstrating the power of family, love, and loyalty.

It is safe to say that such a believable portrayal of family dynamics comes from the relationships on the set. And that statement is backed up by the interviews the cast has given over the years.

There's nothing more heartwarming for fans than reading about the close, almost familial relationships on the set of the beloved show. And perhaps the most touching confirmation of this came from Donnie Wahlberg, who plays Danny Reagan, the eldest Reagan sibling.

During the emotional interview with ET after his mother Alma passed away, Wahlberg recalled how his Blue Bloods family supported him during hard times and how much it meant to him.

He also shared that he had a special bond with Tom Selleck, who portrays family patriarch Frank Reagan in the series.

"I call him dad now, and he calls me son. I mean, that's how we talk to each other off-camera," the actor said.

Of course, this special bond was not born on day one, even though Donnie felt a special connection to the Reagan family from the first time he saw the script.

The actor, who comes from a large family with nine children, immediately identified with his Blue Bloods character and saw his own father in Frank. But Selleck was not so quick to jump into the whole father-son dynamic.

"First he used to kind of grumble at me, like... 'This music guy's kind of weird.' And then now he calls me son," Wahlberg recalled.

Today, Selleck has become a real father figure to Donnie Wahlberg and the rest of the cast. According to them, he is as much a leader on the set as he is a loving parent who gives them hugs.

"You know, you get a hug out of Tom Selleck, that's a big deal," Donnie said.