Identity Crisis

My older biological sister and younger biological brother and I were adopted when we were very young, my brother a year or two old and I a year older than him, and my sister two years older than me. We've known we've been adopted ever since we knew the meaning of adoption. We are the youngest among 9 children. I used to have a twin that died when she was a baby. My biological mother died because she was ill shortly after my brother was born. My biological father gave us up because he couldn't care for us. He's poor and taking care of 8 children was too much for him.

I love the family I have, my parents have raised me, they have loved me and given me all I need. My parents are very open about my decision to see my biological family. However, my mother does not recommend for me to see my older biological brothers. She said something like, "They were really tough and rough. I don't trust them." I don't know much more.

The eldest sibling is about 12 years older than me. I had no interest in ever meeting my biological siblings and biological father. But over time I've been asking more and more questions about who I am. And I don't know where to find the answers without needing to meet my biological family.

During the summer of 2009 I was out of the country visiting relatives. All of my biological siblings appeared at my house in my home country demanding to see us. I was hurt and offended. What right did they have to simply come back into my life? I mean, they have their own kids, their own families, why come now, of all years? They could have visited regularly or earlier on. But what hurt most was the disrespect. I would have expected them to ask for permission and see if we shared the same longing of seeing each other (which I obviously don't). It hurt and I got offended and it just ticked me. I just wanted them to get out of my life. I was happy I was out of the country.

They might be siblings by blood. But that doesn't erase the fact that they are strangers. I don't want to be a part of their life. I don't want them to be a part of my life. I'm happy with where I am, I'm happy with my family and I'd prefer that they not enter my life. But I've been asking myself "Who am I?" How can you know yourself if you don't know a part of your past? Is there a way to move on through the questions of identity without needing to meet my biological family?

I also have trouble sleeping. It takes me hours to fall asleep and when I do, I don't remember any dreams. I only remember nightmares, and those are remembered with vivid detail. I grind my teeth in my sleep and have been grinding them since I was little. I kick and punch in my sleep as well. I've gone through multiple depression phases, and I've struggled with suicidal thoughts. All of this, I've been told can be caused because of experiences before being adopted. Is this possible?