For me, my "high needs" babies both needed to be held constantly, had trouble settling or sleeping on their own, were refluxy and fussy, etc. From the first night, I haven't been able to get Frankie to sleep on his own without him waking up after 1 or 5 or 10 minutes. He's often grunting, hiccuping, or otherwise uncomfortable. I'm pretty sure it's reflux but my pediatrician is reluctant to prescribe anything for it because he is gaining weight well. (When he's having an especially rough time, he feeds a lot, I think to soothe his throat).
I'm sure all babies are needy in different ways. I mean, they are born with so few "skills" compared to other animals and depend on their caregivers for everything. Fortunately, with my daughter I was able to eventually figure out what worked for her. By 6 months or so, she was sleeping on her own, able to fall asleep independently, etc. At that point her reflux also subsided and she wasn't in pain as much. I had to stick to a strict schedule, but if I did I could manage. She is now very independent and not clingy or needy at all.
I guess there are ways that one's actions can "make" a baby more needy, but I also think infants just come with their own personalities and preferences. I mean, I could decide Frankie just has to tough it out and maybe that would help, but I don't believe in cry-it-out techniques for newborns.
What was your nephew like? Or what did your sister observe that you didn't?
if the pain doesn't settle by mid afternoon I may have to head back in. 
