“Hes got so much hair, his eyebrows are so bushy!”

Donnie Wahlbergis part of a storied police dynasty onBlue Bloods but he didnt immediately see the family resemblance.

But I walked in the room and hes like 64, Im like 511 I think.

Donnie Wahlberg and Tom Selleck

Donnie Wahlberg and Tom Selleck.Vera Anderson/WireImage

The height was far from the only issue in Wahlbergs estimation.

I didnt even care about the mustache, I was like, How am I this dudes son?

I was like, Theyre gonna fire me tomorrow.

Vera Anderson/WireImage

It was only after Wahlberg met the actor behind another key Reagan that his anxieties dissipated.

I was like, Alright, I got his genes.

She said Can you be in New York tomorrow?

You’re on a show calledBlue Bloodsand it’s been picked up.'

I was like, When this boat comes into port I’m getting on the first plane.

I’ll be there.

Blue Bloodsairs Fridays at 10 p.m. ET/PT on CBS.

you’ve got the option to watch the fullBrotherly Loveinterview above.