Adv.Marc.iv.19;Panarion 42
Note that the Catholic inserted Luke 8:19:20 And it was told him by certain [people] which said,
Thy mother and thy brethren stand without,
desiring to see thee.
21 And he answered and said unto them,
[ Who is] My mother and my brethren?
My mother and my brethren are these
which hear My words, and do [them]
Now Jesus' mother and brothers came to see him, but they were not able to get near him because of the crowd
What is striking, however, in the sentence:
Thy mother and thy brethren stand without, desiring to see thee.
is that it appears that the alleged false mother and those alleged false brothers had already been identified, and placed in a definite point of space and time.
This shows then what?
To my eyes, only the natural consequence of the erroneous conception about Jesus's identity.
If Jesus is a man, then he must have a particular mother and particular brothers (as having already been identified the father Joseph - by the inhabitants of Capernaum, at incipit of Evangelion - there is no need to repeat the name of Joseph), hence the denial of the conclusion by Jesus brings to deny the same premise: if Jesus did not have mother and brothers, then Jesus is not a man.
After all, that Jesus was invited to recognize those who are outside as his alleged mother and alleged brothers corresponds to a test with an uncertain outcome.
In the sense that the author of the test, or who intends to test Jesus, even if he already is persuaded about the (wrong) identity Jesus == the Messiah Son of Josep, is missing only the direct confirmation of the concerned individual. The need for confirmation by Jesus proves the purely hypothetical nature of the test, in other words, who is making the statement:
Thy mother and thy brethren stand without, desiring to see thee.
is not really sure about what he is stating.
But the proto-catholic Luke inserted 8:19:
Now Jesus' mother and brothers came to see him, but they were not able to get near him because of the crowd
in order to show as a pure and simple FACT a priori that these people were real mother and brothers of Jesus. This becomes not more a test about the real identity of Jesus, but about the mere mental sanity of Jesus.