Douay-Rheims
[21] And when his friends had heard of it, they went out to lay hold on him. For they said: He is become mad.
[31] And his mother and his brethren came; and standing without, sent unto him, calling him.
King James:
21 And when his friends heard of it, they went out to lay hold on him: for they said, He is beside himself.
31 There came then his brethren and his mother, and, standing without, sent unto him, calling him
So the people who thought He was mad may not have even been family at all, but they were definitely not His mother and brothers, who arrived 10 verses later even in your translation.
So we still don’t know why His mother and brothers were there.
And again:
35 Whoever does the will of God is my brother and sister and mother. Jesus Himself uses these words to describe people who are NOT his brothers or sisters or mother, so they cannot always be taken literally.
Love,
O2
It is exactly because the two applications are apposite in Jesus' use to illustrate that in the mention of His family without, their relationship to him must be quite solidly literal language; whereas the imputed relationship of true believers in the Kingdom of God is then figurative-literal language, in both cases comprising and corresponding to a literal interpretation of the scripture under consideration.
When the people of Jesus' synagogue (as well as Pharisees) showed their discomfiture at Jesus' claiming to be a prophet (Israel had been without a prophet for 400 years) they said that he was Joseph and Mary's son (Lk. 4:22, Jn. 6:42), and the brother of Simeon, James, Judah, and Joses (Mt. 13:55, Mk. 6:3). When the plain sense makes common sense, hermeneutics says seek no other sense.
(Of course when Jesus held up the bread and said, "This is my body," that does not make common sense, does it? Therefore it is not plain sense, either, according to all human experience, so a figurative sense must be sought.)
So, When Joseph, Mary, Jesus, Joses, Juda, James, Simon, and His sisters are all plainly known to be one family by their acquaintances, common sense says they are all Mary's children, and there is no reason to seek some other unobvious interpretation, is there?
You need to deck the idea of perpetual virginity forMary of Nazareth, Joseph's wife: "And knew her not till she had brought forth her firstborn son . . ."