Mary - "ever-virgin"
499 The deepening of faith in the virginal motherhood led the Church to confess Mary's real and perpetual virginity even in the act of giving birth to the Son of God made man. 154 In fact, Christ's birth "did not diminish his mother's virginal integrity but sanctified it." 155 And so the liturgy of the Church celebrates Mary as Aeiparthenos , the "Ever-virgin". 156
500 Against this doctrine the objection is sometimes raised that the Bible mentions brothers and sisters of Jesus. 157 The Church has always understood these passages as not referring to other children of the Virgin Mary. In fact James and Joseph, "brothers of Jesus", are the sons of another Mary, a disciple of Christ, whom St. Matthew significantly calls "the other Mary". 158 They are close relations of Jesus, according to an Old Testament expression. 159
501 Jesus is Mary's only son, but her spiritual motherhood extends to all men whom indeed he came to save: "The Son whom she brought forth is he whom God placed as the first-born among many brethren, that is, the faithful in whose generation and formation she co-operates with a mother's love." 160
Mary's virginal motherhood in God's plan
502 The eyes of faith can discover in the context of the whole of Revelation the mysterious reasons why God in his saving plan wanted his Son to be born of a virgin. These reasons touch both on the person of Christ and his redemptive mission, and on the welcome Mary gave that mission on behalf of all men.
503 Mary's virginity manifests God's absolute initiative in the Incarnation. Jesus has only God as Father. "He was never estranged from the Father because of the human nature which he assumed. . . He is naturally Son of the Father as to his divinity and naturally son of his mother as to his humanity, but properly Son of the Father in both natures." 161
504 Jesus is conceived by the Holy Spirit in the Virgin Mary's womb because he is the New Adam, who inaugurates the new creation: "The first man was from the earth, a man of dust; the second man is from heaven." 162 From his conception, Christ's humanity is filled with the Holy Spirit, for God "gives him the Spirit without measure." 163 From "his fullness" as the head of redeemed humanity "we have all received, grace upon grace." 164
505 By his virginal conception, Jesus, the New Adam, ushers in the new birth of children adopted in the Holy Spirit through faith. "How can this be?" 165 Participation in the divine life arises "not of blood nor of the will of the flesh nor of the will of man, but of God". 166 The acceptance of this life is virginal because it is entirely the Spirit's gift to man. The spousal character of the human vocation in relation to God 167 is fulfilled perfectly in Mary's virginal motherhood.
506 Mary is a virgin because her virginity is the sign of her faith "unadulterated by any doubt", and of her undivided gift of herself to God's will. 168 It is her faith that enables her to become the mother of the Savior: "Mary is more blessed because she embraces faith in Christ than because she conceives the flesh of Christ." 169
507 At once virgin and mother, Mary is the symbol and the most perfect realization of the Church: "the Church indeed. . . by receiving the word of God in faith becomes herself a mother. By preaching and Baptism she brings forth sons, who are conceived by the Holy Spirit and born of God, to a new and immortal life. She herself is a virgin, who keeps in its entirety and purity the faith she pledged to her spouse." 170
154 Cf. DS 291; 294; 427; 442; 503; 571; 1880.
155 LG 57.
156 Cf. LG 52.
157 Cf. Mk 3:31-35; 6:3; 1 Cor 9:5; Gal 1:19.
158 Mt 13:55; 28:1; cf. Mt 27:56.
159 Cf. Gen 13:8; 14:16; 29:15; etc.
160 LG 63; cf. Jn 19:26-27; Rom 8:29; Rev 12:17.
161 Council of Friuli (796): DS 619; cf. Lk 2:48-49.
162 1 Cor 15:45,47.
163 Jn 3:34.
164 Jn 1:16; cf. Col 1:18.
165 Lk 1:34; cf. Jn 3:9.
166 Jn 1:13.
167 Cf. 2 Cor 11:2.
168 LG 63; cf. 1 Cor 7:34-35.
169 St. Augustine, De virg. , 3: PL 40, 398.
170 LG 64; cf. 63.
Perpetual Virginity - Catechism of the Catholic Church