The Alpha's Sister

I looked over at my sister and froze, before screaming out in pain. I bit my tongue to keep from screaming as I felt my lungs constrict to the point where I couldn't breathe. As pack Alpha, I had to be strong. After a few minutes the pain subsided, and I looked at the alert faces of every pack member. I assured them I was okay before looking at my 18 year old sister, and I knew she felt the pull between us. And I knew she felt the horror I felt, at knowing that my blood sister and I were mates.