We have a video I should post of when Roscoe met Finley for the first time. He (Roscoe) stayed at some of our friends while we were in the hospital and came back after we had a chance to get home and get a little settled. Finley was asleep in the little lamb bouncer/chair and Miles held Roscoe by the collar as he walked him up to meet baby brother. I thought that Roscoe would be more curious, but he just went up to him, sniffed him and then walked away totally unfazed as if he already knew Finley. It was if he was saying, "yeah I know this guy - I've known him for the last nine months. No big deal."
And that's what it's been ever since - no big deal. Finley now crawls all over him, pulls at his ear, grabs his paws, follows him around, etc and Roscoe is just as patient and loyal as ever. Every baby needs a Roscoe.