Who is a brother, sister and mother

Matthew 12:46-50
[46]Jesus was still talking to the people when his mother and brothers arrived. They stood outside, asking to speak with him.
[47]So one of the people there said to him, “Look, your mother and brothers are standing outside, and they want to speak with you.”
[48]Jesus answered, “Who is my mother? Who are my brothers?”
[49]Then he pointed to his disciples and said, “Look! Here are my mother and my brothers!
[50]Whoever does what my Father in heaven wants him to do is my brother, my sister, and my mother.”