While he was busy with ministry work, his mother and his brothers came, and standing outside, they sent word to Jesus and called him trying to interrupt what he was doing. Mark 3:21 says, "...his family...set out to restrain him, because they said, "He's out of his mind." He is beside himself.
They thought they had a claim on Him taking precedence over other matters. If you’re a preacher you know what I’m talking about, how your family comes, and they send word for you, and say call him/her to us. But Jesus said, whoever does the will of God, he is my brother and sister and mother.
He’s not dishonouring family values that God established at creation, but is simply asserting that physical relationship is not the proper access to Him, but doing the Father’s will gives evidence that one is properly related, "For whosoever shall do the will of my Father which is in heaven, the same is my brother, and sister, and mother" Matthew 12:50.
Simple Gospel Summation.