I mean, I wouldn’t expect consistency here. In fact, a lot of the argument in favor of a historical Jesus is that the story doesn’t make much sense unless they were trying to work around inconvenient facts about an actual person. Kinda like how L Ron Hubbard has a story about how he saved a young woman from a satanic cult (in actuality, he stole Jack Parsons’ girlfriend and life savings).
If you want an apologist answer, then it’s that both Mary and Joseph were descended from David. Several generations removed, mind you. They weren’t closely related as far as we know.
Matthew and Luke both give alternate genealogies, and apologists say that one is for Mary and the other for Joseph. Which one is which isn’t clear. These are usually the same people saying that you can’t read between the lines of the Bible; you must take the words as they are. And yet, you can’t reconcile those two genealogies without somehow assuming something that isn’t in the text.