The 82-year-old legendary actress has paid a touching tribute to Jackie, who died from breast cancer on September 19, on her official website, reported Female First.
Joan recalled the moment Jackie revealed her stage four breast cancer news to her - seven years after being diagnosed.
"My voice was so choked with tears I could hardly speak. She explained that since we spent so much time in Europe while she was in LA, she knew I would be worried but there would be nothing I could do.
The "Dynasty" star also told of her deep sadness at the loss of Jackie, who was 77 at the time of her death.
"I don't think I will ever recover from the sadness of losing my beautiful baby sister. Someone once said, 'The reality is that you don't 'get over' the loss of a loved one, you learn to live with it.'