Is it illegal to use a false Social Security number to get married and would it be a legal marriage?

Most definately! Look at the question and try to say no. Anytime you falsify anything against the government you can be arrested and jailed if the respective entity finds out. That's the reason why at the bottom of virtually almost all legal documents it states "I certify under penalty of perjury that the foregoing is TRUE and CORRECT." PERJURY DEFINED: Perjury is the act of lying or making verifiably false statements on a material matter under oath or affirmation in a court of law or in any of various sworn statements in writing. Perjury is a crime because the witness has sworn to tell the truth and, for the credibility of the court, witness testimony must be relied on as being truthful. Perjury is considered a very serious crime as it could be used to usurp the power of the courts, resulting in miscarriages of justice. In the United States, for example, the general perjury statute under Federal law provides for a prison sentence of up to five years, and is found at 18 U.S.C.