Family History of Glaucoma

I am a "glaucoma suspect" on Lumigan. I was 21 years old in 1991 when I was diagnosed as a suspect, and from 1999 up to now, I am using anti-glaucoma medication. I have high eye pressure but no damage.
My mother went to the eye doctor recently and he said he found an area that has damage which looks like glaucoma. He gave her a field vision test, and said the damage match the area that she missed on the field vision test. She is going back to him later this month for another field vision test to make sure it is a fluke or not. Doctor said if this test is positive, she will be put on drops like me. She has damage but her eye pressure is normal.
My great-grandmother (Mom's grandmother) was blind from glaucoma for several years until her death...and great-grandmother had a couple of relatives (uncle, aunt, a couple of cousins) around the 1800s and/or turn of the century 1900s that had glaucoma. But I don't know if theirs is like mine (high eye pressure) or like Mom's (normal pressure). Mom also have Macular Degeneration. She is 59 years old and I am 33 years old.
My question is: Is it possible to have the opposite problem in the same family? I know I have a very good chance of getting glaucoma like my mother has....but our pressure level was the opposite from each other.
Thanks to any of you who have answered my question.

Nancy