It does count if your great-grandfather is deceased. You will need to know which Lodge he belonged to (a dues card might be helpful, but I am not sure it is necessary). To join, contact the chapter closest to you. Since your profile says you are in Alabama, you can go to the Alabama OES website (
http://members.aol.com/alaoes/) and find the closest chapter and their contact information, if you do not know it already. The Worthy Matron or Secretary would probably be the best people to contact, though any member can help you with the process. First they will have you fill out a membership application known as a petition. Then you will meet with a few members, be voted on, and hopefully intitated.
Hope this helps!