I do think there is such a thing as a hardgainer, but it's just a matter of out-eating your metabolism. I was extremely scrawny most of my life, but I felt like I was eating enough food (I did not feel hungry very often).
Until the age of 31, I weighed about 127-130 (at 5'11+"). I've been active by playing sports and keeping active most of my life, but never felt I could gain weight. When I was a teenager I lifted weights but with the attention span of a toddler, after not getting results in a few days/weeks, I threw in the towel.
Well, that was three years ago, now I'm about 188-190. The first 30 pounds was pretty easy, within about 9 months of training I had hit 150, and finally felt 'normal'.
I had to eat until I felt like puking, it's gotten better now, but if I drop back to a 'normal' diet, I start shedding pounds pretty quickly. unfortunately, it doesn't seem like my bodyfat levels drop when those few pounds come off.
In three years I have not really done any 'cutting' as I'm afraid to lose the muscle and strength gains I've worked so hard for, but I have accumulated more abdominal fat than I would prefer.