A third objection to the perpetual virginity of Mary arises
from the use of the word, prototokos, translated "first-born"
in Luke's gospel.
Luke 2:7
(Mary) gave birth to her firstborn son (prototokos). She
wrapped him in swaddling clothes and laid him in a
manger ...
The Greek word prototokos is used of Christ as born of Mary
and of Christ's relationship to
His Father (Col 1:25). As the
word does not imply other
children of God the Father, neither
does it imply other children of
Mary. The term "first-born" was
a legal term under the Mosaic
Law (Ex 6:14) referring to the
first male child born to Jewish
parents regardless of any other
children following or not. Hence
when Jesus is called the
"first-born" of Mary
it does not mean that there were second
or third-born children.