I'm pretty sure the "Man boobs" comes from being a bit obese and such. As far as the nipple thing I think its genetics, and pec development through compound and isolation exercises, pretty sure its genetic too, I don't really know what "over developed pec" means, but some guys just have boob looking pecs even if there chest muscles aren't really that big, my cousin is one. We both go to the gym together for years and hes constantly complaining about his pecs being to "oval" or cicle shaped.
I personally don;t think it looks weird, were all unique in our own way even in bodybuilding, like traps for example, some people look like freaking cobras, some people barely have them. Same thing with pecs, some guys just have the most "booby" looking chest out there, regardless of there exercise routine.