I Don't Know My Mother's Parents

I am 15 years old and I still do not know my grandparents. When I was little, my parents lived with my grandfather, but they quarreled badly and still do not look at each other. I do not know him. And when my mother was a baby, her father divorced his wife and so she found another and now she is not "part of the family" at all. I have no right to go to that town where my mother grew up alone. Fortunately for my mother, my mother (I can't call her grandmother) has a sister who is married. She and her family love us very much and rarely come to see us because we live a long distance away. Once they were our guests, I found out more about my mother's mother. She had a child who was my mother's set and seemed to be married. I really want to see and talk to them, but there is no way! Can you think of a safe way to do it without my parents knowing It is not right for me to be hidden from my family. I forgot to say, I know how his Facebook is.