If Peter's youngest son was born in 1957, then he [Peter]would have been born prior to 1940 and he should appear on the 1940 census. I did not find him with parents, Ernest and Mattie. Where did you find those names? Also, have you looked at the birth certificates of Toni and Terry? Their father's name, age and place of birth should be listed. That info is given on my certificate. Have you tried getting a death certificate for Peter? The Social Security Administration might be another avenue if he died around 1960.
I assume that Ruth is deceased and can't provide information.
I'm sorry I've been of no help. If I think of something else to research, I'll do so.