[RnMomof7]

Do you understand the context of that quote? It was a rebuke to His mother..

His mother and brothers were interrupting his teaching and so this was His response

Mark 3:31 And his mother and his bretheren came; and standing without, sent unto him, calling him. 32 And the multitude sat about him; and they say to him: Behold thy mother and thy brethren without seek for thee. 33 And answering them, he said: Who is my mother and my brethren? 34 And looking round about on them who sat about him, he saith: Behold my mother and my brethren. 35 For whosoever shall do the will of God, he is my brother, and my sister, and mother.

In other words we that come in faith as the Father wills are as dear to Him and as loved by His as His mother and family

This is not declaring her our mother

[A.A. Cunningham]

It was a rebuke to His mother..

That's your own personal interpretation.

[BenKenobi]

“And the multitude sat about him; and they say to him: Behold thy mother and thy brethren without seek for thee.”

You need to read your own quote. He’s addressing the multitude. He’s not rebuking his mother. This is why he says, whomever follows the word of God, is my brother, and mother and sister.