Robert Rayburn summarizes simply the use of “until” in Matthew 1:25:
The natural sense of the “until” is that Joseph and Mary had a normal married life after Jesus was born, contrary to the Roman Catholic doctrine of Mary’s perpetual virginity. The natural sense of Jesus being called her “firstborn” in Luke is that Mary had other children and that the “brothers” of Jesus mentioned in Matt. 12:46 were also her children by Joseph, also contrary to the notion that she remained a virgin the rest of her life.
