Both Luke and Matthew give detailed genealogies of Joseph, going back to Abraham in Matthew, and to Adam in Luke. However, apart from Abraham, Isaac and David, very few names appears on both lists. Presumably, no Christian ever bothers to read these lists, otherwise someone would have spotted it by now. Perhaps some Christians spot it but they're scared that they'll go to Hell if they dare to doubt.
What is also not explained is why a genealogy of Joseph should appear, as he is not supposed to be the father of Jesus - it is completely irrelevant, as Joseph apparently never touched Mary, certainly not with that, anyway!