Hi Virginia and Welcome to WikiTree
You have a good start looking for cousins, you put tags on your question so the right people will look.
Have you looked for your great grandparents in WikiTree. You can do that by using the Find menu and clicking on Search.
Another way is to use Find and click on Surnames. Then you get a list of all the profiles on WikiTree with the surname you want. You can sort the list by date or by first name,
Good luck searching and come back here with more questions anytime.