Mary

97. How does Mary cooperate in the divine plan of salvation?
493-494
508-511
By the grace of God Mary was kept free from every personal sin her whole life long. She is the one who is “full of grace” (Luke 1:28), “the all holy”. When the angel announced to her that she would give birth to “the Son of the Most High” (Luke 1:32), she freely gave her consent with “the obedience of faith” (Romans 1:5). Mary thus gave herself entirely to the person and work of her Son Jesus, espousing wholeheartedly the divine will regarding salvation.
98. What does the virginal conception of Jesus mean?
496-498
503
The virginal conception of Jesus means that Jesus was conceived in the womb of the Virgin solely by the power of the Holy Spirit without the intervention of a man. He is the Son of the heavenly Father according to his divine nature and the Son of Mary according to his human nature. He is, however, truly the Son of God in both natures since there is in him only one Person who is divine.
99. In what sense is Mary “ever Virgin”?
499-507
510-511

Mary is ever virgin in the sense that she “remained a virgin in conceiving her Son, a virgin in giving birth to him, a virgin in carrying him, a virgin in nursing him at her breast, always a virgin” (Saint Augustine). Therefore, when the Gospels speak of the “brothers and sisters of Jesus”, they are talking about the close relations of Jesus, according to the way of speaking used in Sacred Scripture.