What He says in that passage is that all who keep His word are His brethren, and Mary's children. He repeated that point more forcefully on the Cross. "Behold, your son". This made us all her children:
the dragon was angry against the woman: and went to make war with the rest of her seed, who keep the commandments of God, and have the testimony of Jesus Christ.(Apoc. 12:17)
In any case, his mother and his brothers were outside seeking to speak to him. He was told this. He then spoke spiritually when he said, indicating the crowd, that "these" are my brothers and mother.
The contrast is between Mary and his brothers and those in the crowd who are his spiritual brothers and mother.
Mt 13:55 - Is this not the carpenter's son? Is not His mother called Mary? And His brothers James, Joses, Simon, and Judas?
Mt 12:46 - While He was still talking to the multitudes, behold, His mother and brothers stood outside, seeking to speak with Him.
Mt 12:49 - And He stretched out His hand toward His disciples and said, "Here are My mother and My brothers!
In the following passage, the child is taken to heaven, but the woman remains on earth. This denies the Assumption, doesn't it? In fact, it is not about Mary at all.
1 A great and wondrous sign appeared in heaven: a woman clothed with the sun, with the moon under her feet and a crown of twelve stars on her head. 2 She was pregnant and cried out in pain as she was about to give birth. 3 Then another sign appeared in heaven: an enormous red dragon with seven heads and ten horns and seven crowns on his heads. 4 His tail swept a third of the stars out of the sky and flung them to the earth. The dragon stood in front of the woman who was about to give birth, so that he might devour her child the moment it was born. 5 She gave birth to a son, a male child, who will rule all the nations with an iron scepter. And her child was snatched up to God and to his throne. 6 The woman fled into the desert to a place prepared for her by God, where she might be taken care of for 1,260 days.