Is it permissible to deceive a girl's family into believing I am of their religion in order to marry her, and does this violate Sharia?

It is impermissible to deceive the family of a non-Muslim girl by pretending to be of their faith in order to marry her, for two reasons: First, it is not permissible for a Muslim to claim disbelief, whether jokingly or seriously, based on the Almighty's saying: {And if you ask them, they will surely say, "We were only conversing idly and playing." Say, "Is it Allah and His verses and His Messenger that you were mocking?" Make no excuse; you have disbelieved after your belief}. Second, lying to and deceiving non-believers is not permissible except in warfare, for war is deception.