Both of his parents were US Citizens when he was born?
Rubio’s parents were not citizens when he was born. He is not a NBC.
http://www.freerepublic.com/focus/news/2840767/posts?page=90#90
The Constitutional Meaning Of “Natural Born Citizen”
Vanity Essay | 31 January 2012 | sourcery
This says it better than any other one source that I know of on FR.