Hi, my name is Annette. Your great grandfather Jeyou "Gee" Smack married Georgianna nee Brittingham Smack. Your great grandfather's father, William Gordon Smack and my paternal grandfather, John Alfred Smack were brothers. I do not know of any other children your great grandfather had other than the ones you named.
I have additional information on this line of the Smack family if you are still interested.