Several places in the New Testament there is reference to the brothers and/or sisters of Jesus. The brothers are named, the sisters are not. Does this imply that “sisters” means fellow female Christians – or that he had biological sisters who are not named (do we know their names?)?
Yes, Jesus did have brothers and sisters. Matthew 13:55,56 says, “Is not this the carpenter’s son? is not his mother called Mary? and his brethren, James, and Joses, and Simon, and Judas? And his sisters, are they not all with us? Whence then hath this man all these things?” Mark 6:3 says, “Is not this the carpenter, the son of Mary, the brother of James, and Joses, and of Juda, and Simon? and are not his sisters here with us? And they were offended at him.”
It is not uncommon in the Bible for only the sons to be named, and not the sisters. The Bible starts right out that way, naming Cain, Abel, and Seth, but none of Adam and Eve’s daughters (which is where their sons got their wives). The family name is carried on through the sons, not the daughters. This does not mean that boys are more important than girls in God’s eyes; but remember, the Bible deals with about 4,000 years of history. Not everyone’s name could be recorded, or else the whole Bible would have read like the first several chapters of I Chronicles.