Here is Tertullian’s position wrt the PV of Mary:
- To what purpose could they have tempted Him by naming His mother and His brethren? If it was to ascertain whether He had been born or not–when was a question raised on this point, which they must resolve by tempting Him in this way? … Even if it had been necessary that He should thus be tried in the investigation of His birth, surely any other proof would have better answered the trial than that to be obtained from mentioning those relatives which it was quite possible for Him, in spite of His true nativity, not at that moment to have had. For tell me now, does a mother live on contemporaneously with her sons in every case*? Have all sons brothers born for them? …… If, therefore, He made them “His mother and His brethren” who were not so, how could He deny them these relationships who really had them? Surely only on the condition of their deserts, and not by any disavowal of His near relatives; teaching them by His own actual example, that “whosoever preferred father or mother or brethren to the Word of God, was not a disciple worthy of Him.” Besides, His admission of His mother and His brethren was the more express, from the fact of His unwillingness to acknowledge them. That He adopted others only confirmed those in their relationship to Him whom He refused because of their offence, and for whom He substituted the others, not as being truer relatives, but worthier ones. Finally, it was no great matter if He did prefer to kindred (that) faith which it did not possess. Against Marcion IV .19
here Tertullian, in the context of discussing Jesus’ mother and brethren asks “does a mother live on contemporaneously with her sons in every case?” By so doing he designated the brethern of Jesus to be Mary’s sons…now if you want to interpret Tertullian’s wording to mean that he believed Mary had sons by way of the pre-existing children of Joseph, it’s possible, though more than he explicitly says and unlikely given his choice of words.
But let Apelles, as well as Marcion, hear from me what was the reason behind the reply which for the moment denied mother and brethren. Our Lord’s brethren did not believe in him: this also is included in the Gospel as it was published before Marcion’s day. His mother likewise is not shown to have adhered to him, though Martha and other Marys are often mentioned as being in his company. At this juncture their unbelief at last comes into the open. When Jesus was teaching the way of life, when he was preaching the Kingdom of God, when he was occupied in healing infirmities and sicknesses, though strangers were intent upon him these near relations were absent…‘Who is my mother, and who are my brethren?’? When Christ was preaching God and giving proof of him, was fulfilling the Law and the Prophets, and was dispelling the darkness of long ages past, was it without justification that he used this expression to castigate the unbelief of those who stood without, or at least to expose their unseasonableness in calling him back from his work? On the Flesh of Christ 7
**here Tertullian indicated a lack of evidence of Mary’s adherence to Jesus, thereby questioning her faithfulness to the Lord at the time of John 7:5…Why do venerators say God ensured the perpetual virginity of Mary? Isn’t a main reason to emphasize her absolute purity?..something entirely at odds with questioning her faithfulness to the Lord. Do you really think that Tertullian would call into question Mary’s faithfulness and still feel the need assert her virginity after Christ’s birth? **
She who bare (really) bare; and although she was a virgin when she conceived, she was a wife when she brought forth her son.* Now, as a wife, she was under the very law of opening the womb, *** wherein it was quite immaterial whether the birth of the male was by virtue of a husband’s co-operation or not;** it was the same sex that opened her womb**. Indeed, hers is the womb on account of which it is written of others also: Every male that opens the womb shall be called holy to the Lord. On the Flesh of Christ 23
Here Tertullian declares his belief in Mary’s virginity at conception and indicates that the birth process opened her womb …no virginity in partu
Turning now to the law, which is properly ours— that is, to the Gospel— by what kind of examples are we met, until we come to definite dogmas? Behold, there immediately present themselves to us, on the threshold as it were, the two priestesses of Christian sanctity, Monogamy and Continence: one modest, in Zechariah the priest; one absolute, in John the forerunner: one appeasing God; one preaching Christ: one proclaiming a perfect priest;…For who was more worthily to perform the initiatory rite on the body of the Lord, than flesh similar in kind to that which conceived and gave birth to that (body)? And indeed it was a virgin, about to marry once for all after her delivery, who gave birth to Christ, in order that each title of sanctity might be fulfilled in Christ’s parentage, by means of a mother who was both virgin, and wife of one husband. On Monagamy 8
Here Tertullian sounds as if he is putting forward a view similar to Helvidius’s (as described by Jerome)…namely that Mary held both of the titles of sanctity by being both the virgin and the wife (a wife being a non-virgin, as being under the very law of opening the womb).