Searching for birth family-Born 6/27/69

I am looking for my sister, she may not even know that she was adopted. My mother had 3 daughters. The middle child was adopted out. The sister that I am searching for was born in 1969 in New Orleans. My older sister found her birth certificate in a closet. I was only 9 years old when I had the birth certificate in my hand and I can't remember much. I can only remember that she was not quite 2 years older than me. There was also a picture of her. She was about 6 months old when she was placed for adoption. I am not sure which agency was used. One relative told me that it was Catholic Charities and another told me VOA and our birthmom told me it was not either. Probably to throw me off. Our mom is holding out on me! I am fairly certain that she is a full sister because my father's name was on the BC but there appears to be some controversy between my mom and dad over that which lead to a protective order and my mother sheltering. Also, she could have been a ward of the court. From what our birth mom says....the adoption was forced. My mother sheltered with this child with a protective order against my father. When the two made back up, the state took custody. I was conceived after all of this was said and done. If she does know that she is adopted, she may not even know about me, since I was delivered after her adoption. My mother is alive and well but my dad passed away when I was 13.