Why did the Blessed Virgin Mary marry? According to Catholicism, why did the Blessed Virgin Mary, who intended to remain a virgin, marry St. Joseph?
According to ch. 6 of Brown, O.F.M.'s The Life of Mary as Seen by the Mystics, a compilation of the approved private &quot;Revelations of St. Elizabeth of Schoenau, St. Bridget of Sweden, Ven. Mother Mary of Agreda and Ven. Anne Catherine Emmerich,&quot; she married because her parents died and young girls' service in the Temple was not perpetual:

WHEN MARY reached the age of thirteen and a half, having grown considerably for her age, Almighty God in a vision commanded her to enter the state of matrimony. Because of her intense love of chastity and her early vow of perpetual virginity, which she had often renewed, this divine order meant to her a sacrifice as painful as that of Abraham when God commanded him to offer up his son’s life.
When Mary heard this unexpected decree, she was astonished and became greatly afflicted. Nevertheless she prudently suspended her own judgment and preserved her faith and hope more perfectly than Abraham. Still hoping against hope, she meekly replied:
“Eternal God, Thou, O Lord, canst dispose of me, Thy worthless little worm, according to Thy pleasure, without making me fail in what I have promised. And if it be not displeasing to Thee, my good Lord, I renew my desire to remain chaste during all my life.”
Thus Mary in her great trial, though she felt some human uneasiness and sadness, obediently resigned herself entirely to the Will of God. And the Lord answered her:
“Mary, let not thy heart be disturbed, for thy resignation is acceptable to Me. And by My disposition, that will happen which is best for thee.”
Then, as God intended, while left between uncertainty and hope, Mary gave herself over to fervent prayer and inner acts of love, faith, humility, obedience and chastity.
Meanwhile the Lord spoke in sleep to the High Priest, who happened to be St. Simeon, and commanded him to arrange the marriage of Mary, whom He regarded with special love, to whomever it seemed right to the council of priests. After consulting together, the priests appointed a day on which all the bachelors of the line of David, which was also Mary’s, were to assemble in the Temple.
Nine days before that date, Simeon called in Mary and gently explained to her that as she was an orphan and a first-born daughter with an inheritance, now near the age when the young girls had to leave the service of the Temple and marry, the priests were planning to find her a worthy husband. Though deeply moved, Mary replied with great composure and modesty:
“As far as my inclinations are concerned, I desire to preserve chastity during all my life, and I never had the intention to enter the married state. But you, my master, will teach me God’s holy Will.”