Opinions differ as to Christ's canonical genealogy thanks to differing accounts provided within the text of the Bible in the First and Third gospels. This is an ongoing subject for debate between the many different camps of Biblical scholarship and also for rationalist opponents to theological canonicity.
Saint Matthew and Saint Luke present the most immediately conflicting versions of Christ's genealogy. They provide mutually exclusive genealogical trees which converge impossibly when they come to Saint Joseph, postulating him as the patriarch of two distinct lines which go on to reunite in Christ's bloodline. This bone of contention has remained a subject of debate.
Various scholars point to the common practice of omitting figures from Biblical genealogies in order to make them fit symbolically meaningful patterns. This includes the practice of listing genealogies in lots of seven and omitting long, significant stretches of time in order to create a cohesive mythological narrative.
Translation conventions also muddy the issue of Christ's genealogy. Because there is no original text in the Bible's case, authorship being an open question in the case of nearly every one of its books, it is impossible to establish which books are canonical and which are the most firmly rooted in the historicity and context of their time.