John Gill Commentary Mark 3:34

"And looking round on them that sat round about him, he saith, Behold, my mother and my brethren!" — Mark 3:34 (ASV)

And he looked round about on them which sat about him
To find out his disciples among them, and point them out particularly, by stretching forth his hand towards them: and said,

behold my mother and my brethren :
not in a natural, but in a spiritual sense; his mother, because, in regeneration, he was formed in them; his brethren, because, by adoption, his God was their God, his Father their Father; (See Gill on Matthew 12:49).