There are several questions based on Scripture that are often raised by those skeptical about the doctrine of ever-virginity. The first of these involves the passages which state explicitly that the Lord had "brothers." There are nine such passages: Matthew 12:46-47 and 13:55-56; Mark 3:31-32 and 6:3; Luke 8:19-20; John 2:12 and 7:3-5; Acts 1:14; and 1-Corinthians 9:5. The Greek word used in all these passages and generally translated "brother" is adelphos.
The Septuagint, the ancient Greek translation of the Hebrew Scriptures used by the Apostles (abbreviated LXX) includes specific words for "cousin," notably adelphinos and anepsios, but they are rarely used. The less specific word adelphos, which can mean "brother," "cousin," "kinsman," "fellow believer," or "fellow countryman," is used consistently throughout the LXX, even when cousin or kinsman is clearly the relation described (such as in Genesis 14:14, 16; 29:12; Leviticus 25:49; Jeremiah 32:8, 9, 12; Tobit 7:2; etc.). Lot, for instance, who was the nephew of Abraham (cf. Genesis 11:27-31), is called his brother in Genesis 13:8 and 11:14-16. The point is that the commonly used Greek word for a male relative, adelphos, can be translated "cousin" or "brother" if no specific family relation is indicated.
Is there anywhere a clear statement in the Scriptures establishing Jesus brothers as literally the children of Mary? In fact, there is not. Nowhere is Mary explicitly stated to be the mother of Jesus' brothers. The formula for speaking of the Lord's family is "His mother and His brothers." In Mark the possessive, anavtou"of Him," is inserted before both "His mother" and "His brothers," making a clear distinction. In Acts 1:14, the separation is more pronounced: "Mary the mother of Jesus, and His brothers." Some manuscripts use the conjunctive syn "along with, in company with," so that the text reads "Mary the mother of Jesus, along with His brothers." In any case, Mary is never identified as the mother of Jesus' brothers (nor they as her children), but only as the Mother of Jesus.
Also, consider the moving passage from St. John's Gospel in which our Lord commits His Mother into the care of St. John as He dies on the Cross. Why would He do so if she had other children to look after her? Jewish custom dictated that the care of a mother would fall to the second born if the firstborn died, and if the widow had no other child she would be left to take care of herself. Since she is without other children, her Son gives her into the care of the beloved disciple. ~
The Ever-Virginity of the Mother of God — Greek Orthodox Archdiocese of America