But same questions as "Nautilus". If she were pregnant then why marry James? if she were pregnant AFTER marriage that's another story.
But like I said, interesting story. Now, if Lucius believes Sirius then he should take Sirius out of Azkaban too. That will make it more interesting and Harry will have his father. Otherwise knowing Sirius is innocent and still leaving him in prison is a BIG hole in story. Besides it's Lucius. He knows Fudge. He can convince him that he'll be more popular if helps bringing an INNOCENT out.
Just MY thoughts.
Please update soon.
Sirius was given the Dementor's kiss when he was captured. That is why his will was read.