I have never thought of Rob Morrow as a brat pack actor, mainly because I have'nt seen him in any brat pack ensemble-type films.
But I alway enjoy him in Northern Exposure, and QUIZ SHOW is one of my favorite movies.
Rob Lowe, on the other hand---definitely a brat pack guy, yes, but I can't tolerate his "acting". He's done 3 original movie for TNT, including Salem's Lot. I worked on these and never could understand why this guy continues to get work, apart from his looks. (I find Rob Morrow way more attractive, BTW.)
All six seasons of NORTHERN EXPOSURE were filmed here in Washington State. During that time, they employed a great many local actors, both professional and non-professional. I know a large number of actors who worked at various times on the series, and I can tell that the one constant among every single individual, was their intense dislike of Mr. Morrow. At various times I heard him described as vain, self-centered, obnoxious, insensitive, foul-tempered, beliggerant, and a little Hitler. And those are just the terms that I remember.
Personally, I consider Rob Lowe a good actor and Mr Morrow, merely a famous name.