Do other students or professors treat first gen students differently?
Although information about whether a student is a first-generation college/university attendee may appear in some form on the student's application to an institution and may be weighed by the institution in making its admissions offers, there is really no reason that anyone else - students/professors, etc. - would need to be aware of whether a student is first-generation or not. If others are aware of the student's first-generation status, that should not be a factor in how a student is treated, and to my knowledge, it is not. Students establish their own places on a campus by doing well in their classes, becoming intellectually and socially involved, and contributing to the campus environment. The education levels of the student's parents and grandparents is essentially irrelevant.
Having said that, I have visited several institutions which had developed programs intended to meet the needs of first generation students should additional assistance be required in developing various study skills or in supporting certain basic areas of learning - Math, English, etc.. Many schools offer the possibility of this kind of additional assistance to all of their students, however, since it is not just first-generation students who may need this kind of extra help.