Many scholars have replied that Jacob and Heli were half-brothers. Upon Heli’s death without issue, Jacob married his widow in accordance with the Levitical law to provide children to Heli. Joseph would thus be the natural son of Jacob, and the legal son of Heli. In this case, since St. Matt. gives the natural genealogy, and St. Luke the legal genealogy, we have two different yet correct lines of ancestry.
Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty