My youngest son just graduated yesterday. He had 17 family members attend, including 4 grandparents, 5 aunts, 4 cousins, 2 (of 3) siblings and myself and my husband. His class had 18 student graduate so it is a small ceremony and very personalized to all of the class members. The ceremony was about two hours long and included a class historian speech, valedictorian address (my son was the valedictorian), slideshow, presentation of diploma and presentation of awards & scholarships.
Most of these same family members attended both of my older two children's graduations as well. I will definitely be attending my sisters daughters graduation, it's not even a question I'll be there.