We know for sure that neither of Rubio’s parents was a citizen at the time he was born.
If both his parents were LEGAL residents in United States, and if Rubio was born on US soil, then Rubio is NBC based on precedence set by Obama. And Rubio’s birth certificate is not secret, unlike Obama’s which was kept under wraps until Trump made a big stink about it. Many experts have opined that the Obama BC is manufactured. Not so with Rubio’s BC.