When referring to what Jesus taught about family relationships we should be quick to remember how he treated and spoke to his own mother. He called her "woman" at the wedding feast of Canaan. As in, "What is that to me, woman?"
Also we must consider:
Then one said unto him, Behold, thy mother and thy brethren stand without, desiring to speak with thee. But he answered and said unto him that told him, "Who is my mother? and who are my brethren?" And he stretched forth his hand toward his disciples, and said, "Behold my mother and my brethren!" "...For whosoever shall do the will of my Father which is in heaven, the same is my brother, and sister, and mother."
When we speak of the Old Testament Covenant and the requirements of the Law regarding sons --again we are looking at the Torah and the fact that no man can fulfill the law save one. Jesus. It was his heavenly Father who witnessed of him, "Behold my only begotten son in whom I am well pleased."
The lawful requirements of the Old Covenant are all paid by the sacrifice of the Lamb of God on the cross. It is a foundational doctrine we speak of and not any great mystery.
Jesus was speaking to people who thought that they could compel God to return [His presence to the Temple] and establish the Kingdom by their own righteousness and for the sake of their own uprightness. They truly thought they were "on to something here" and wanted to push everybody out of the way, their high and holy way, as they proclaimed themselves to be the salvation hoped for by one and all. He spoke that way to show them they were wrong about that. Jesus was sent to the Lost Children and neither the Pharisees nor their doctrines were the answer. He was. He still is.
~Sparrowhawke