Unfortunately, if there is a female in your Cain line, ie your grandmother, then the Cain Y-DNA has not been passed down to her sons - and DNA testing them will not help. Y-DNA tracks the male/family name line - and so only a man who bears the family name Cain, and whose father was named Cain and whose grandfather... and so on....: possesses the Cain Y-DNA and can be tested. You need a male family member named Cain! Good luck