Dalemar Chadwick

I need to find my brother Dale and sister Margarets ancestry. Anything would help us. We haven't even been able to get a social security number on their dad who died when they were still babies. His name was Dalemer, I'm not sure how youd spell it. When I was a kid and he was married to my mom I called him daddy Dale. His surname was Chadwick. He was in a shootout with the police in Brainard Tennessee and was killed. He was from Marriatta Georgia I believe. Some of his family, Chadwicks, lived and still lives in Rossville Georgia.