Why Did Jesus Have Brothers and Sisters?
Jesus Christ was the firstborn ("she brought forth her firstborn son") child of Mary - who later had other children (see Mary's Other Children):
"2:4 And Joseph also went up from Galilee, out of the city of Nazareth, into Judaea, unto the city of David, which is called Bethlehem; because he was of the house and lineage of David [see also David's Prophecies Of The Christ]: 2:5 To be taxed with Mary his espoused wife, being great with child. 2:6 And so it was, that, while they were there, the days were accomplished that she should be delivered. 2:7 And she brought forth her firstborn son, and wrapped him in swaddling clothes, and laid him in a manger; because there was no room for them in the inn." (Luke 2:4-7 KJV)
Christ was also the firstborn of His Church (see What Is The Church?), from the dead:
"1:18 And he is the head of the body, the church: who is the beginning, the firstborn from the dead; that in all things he might have the preeminence." (Colossians 1:18 KJV)
"8:28 And we know that all things work together for good to them that love God, to them who are the called according to his purpose. 8:29 For whom he did foreknow, he also did predestinate to be conformed to the image of his Son, that he might be the firstborn among many brethren." (Romans 8:28-29 KJV)
"To the church of the firstborn"
Mary was the mother of her firstborn, Jesus, and later other sons and daughters - who were living prophecies of all of His people who will also be born (see the Fact Finder question below) as children of God. For that reason, Mary is used as an analogy for the Church of God, the "woman" from whom God's children (see Spiritual Conception) will be born from the dead (see Born Again, How and When?), just as Christ was (see also The Day Of Christ's Resurrection).
When Satan could no longer destroy Christ, by means of corruption (that's what the "temptation of Christ" was all about - see Could Jesus Have Sinned?), he instead turned on the other "children" who can still be endangered by him, by corruption, because they "keep the commandments of God and have the testimony of Jesus Christ."
"12:13 And when the dragon [see Dragons] saw that he was cast unto the earth, he persecuted the woman which brought forth the man child. 12:14 And to the woman were given two wings of a great eagle, that she might fly into the wilderness, into her place, where she is nourished for a time, and times, and half a time, from the face of the serpent. 12:15 And the serpent cast out of his mouth water as a flood after the woman, that he might cause her to be carried away of the flood. 12:16 And the earth helped the woman, and the earth opened her mouth, and swallowed up the flood which the dragon cast out of his mouth. 12:17 And the dragon was wroth with the woman, and went to make war with the remnant of her seed, which keep the commandments of God, and have the testimony of Jesus Christ." (Revelation 12:13-17 KJV)
The writer of the epistle to the Hebrews (the author is not identified, but many think that it was the apostle Paul; see Epistles) spoke of the "general assembly and church of the firstborn" based upon the facts outlined above.
"12:1 Wherefore seeing we also are compassed about with so great a cloud of witnesses, let us lay aside every weight, and the sin which doth so easily beset us, and let us run with patience the race that is set before us, 12:2 Looking unto Jesus the author and finisher of our faith; who for the joy that was set before him endured the cross, despising the shame, and is set down at the right hand of the throne of God [see What Is Jesus Christ Doing Right Now?]. 12:3 For consider him that endured such contradiction of sinners against himself, lest ye be wearied and faint in your minds.
12:4 Ye have not yet resisted unto blood, striving against sin [see Concupiscence]. 12:5 And ye have forgotten the exhortation which speaketh unto you as unto children, My son, despise not thou the chastening of the Lord, nor faint when thou art rebuked of him: 12:6 For whom the Lord loveth he chasteneth, and scourgeth every son whom he receiveth.
12:7 If ye endure chastening, God dealeth with you as with sons; for what son is he whom the father chasteneth not? 12:8 But if ye be without chastisement, whereof all are partakers, then are ye bastards, and not sons. 12:9 Furthermore we have had fathers of our flesh which corrected us, and we gave them reverence: shall we not much rather be in subjection unto the Father of spirits [see The Holy Father], and live? 12:10 For they verily for a few days chastened us after their own pleasure; but he for our profit, that we might be partakers of his holiness. 12:11 Now no chastening for the present seemeth to be joyous, but grievous: nevertheless afterward it yieldeth the peaceable fruit of righteousness unto them which are exercised thereby.
12:12 Wherefore lift up the hands which hang down, and the feeble knees; 12:13 And make straight paths for your feet, lest that which is lame be turned out of the way; but let it rather be healed [see also The Risen Kingdom].
12:14 Follow peace with all men [see Striving For Strife], and holiness, without which no man shall see the Lord: 12:15 Looking diligently lest any man fail of the grace of God; lest any root of bitterness springing up trouble you, and thereby many be defiled; 12:16 Lest there be any fornicator, or profane person, as Esau, who for one morsel of meat sold his birthright.
12:17 For ye know how that afterward, when he would have inherited the blessing, he was rejected: for he found no place of repentance, though he sought it carefully with tears.
12:18 For ye are not come unto the mount that might be touched, and that burned with fire [see Why Through The Sea?, The Ten Commandments and The Two Great Commandments], nor unto blackness, and darkness, and tempest, 12:19 And the sound of a trumpet, and the voice of words; which voice they that heard entreated that the word should not be spoken to them any more:
12:20 For they could not endure that which was commanded, And if so much as a beast touch the mountain, it shall be stoned, or thrust through with a dart: 12:21 And so terrible was the sight, that Moses said, I exceedingly fear and quake:
12:22 But ye are come unto mount Sion [see Zionism], and unto the city of the living God, the heavenly Jerusalem, and to an innumerable company of angels, 12:23 To the general assembly and church of the firstborn, which are written in heaven, and to God the Judge of all, and to the spirits of just men made perfect, 12:24 And to Jesus the mediator of the new covenant, and to the blood of sprinkling [see Christ's Mercy Seat], that speaketh better things than that of Abel.
12:25 See that ye refuse not him that speaketh . For if they escaped not who refused him that spake on earth, much more shall not we escape, if we turn away from him that speaketh from heaven:
12:26 Whose voice then shook the earth: but now he hath promised, saying, Yet once more I shake not the earth only, but also heaven. 12:27 And this word, Yet once more, signifieth the removing of those things that are shaken, as of things that are made, that those things which cannot be shaken may remain. 12:28 Wherefore we receiving a kingdom which cannot be moved, let us have grace [see Growing In The Grace And Knowledge], whereby we may serve God acceptably with reverence and godly fear:
12:29 For our God is a consuming fire." (Hebrews 12:1-29 KJV)
Fact Finder: For the present time, are Christians born again, or conceived again?
See Conceived Again