An anecdotal reference. Are their children Christian?  Judaism has evangelized more adamantly to maintain Jews within than convert non-Jews without. Evidently, it has been rather successfully that through the centuries and in a variety of cultures and countries Jewish identity has been maintained, despite the minority of Jews who defected. 
A rather remarkable feat given the vicissitudes of the diaspora. Maybe the vicissitudes fostered group cohesion up against a hostile world?