Looking for the Bennett Family IN Ill

My grandfathers name was robert walter Bennett- born may 3 1903. he died in 8,aug 1980 alanta georgia.
He was married to Helen Baum bennett b 1905..died 1967
They had 4 children..David, mary bennett b.oct 15 1936, christine bennett (rothstine),dianne bennett (farrell) not sure on that spelling.
Mary cathrine bennett had a daughter Debra ann Bennett..b may 28 1960
I have my grandfathers line pretty much back but cant find anything on my mother, now decesed or my grandmother..anyhelp would be great.