John Gill Commentary Matthew 12:49

"And he stretched forth his hand towards his disciples, and said, Behold, my mother and my brethren!" — Matthew 12:49 (ASV)

And he stretched forth his hand toward his disciples
By whom are meant, not only the twelve, but all others present, who truly believed in him, both men and women; and who might sit near him and together, and whom, by this motion of his hand, he pointed out as his spiritual relations, to the multitude that sat round him:

and said, behold my mother, and my brethren ;
in whose hearts he was formed, and who were the children of God by adopting grace, and so his brethren; and were as dear to him as his mother and brethren.

It is reasonable to suppose, that when he said, "behold my mother", and, as in the following verse, "sister"; he might stretch forth his hand particularly, toward the pious and religious women that believed in him, and ministered to him of their substance, who might be now present; such as Mary Magdalene, Joanna the wife of Chuza, Herod's steward, and Susanna, and others; since these are mentioned by Luke in the same chapter in which this passage stands in his Gospel; and when he said "behold my brethren", he might point directly to the twelve, and the rest of the men that believed in him, and followed him.