Jesus' family is people who believe Jesus as the Christ. Jn 6:29, 1 Jn 3:23, Jn 3:16, 1 Jn 5:1
Jesus says that those who do the will of God are the family of Jesus. (Mt 12:46-50)
Mt 12:46 While he yet talked to the people, behold, his mother and his brethren stood without, desiring to speak with him. 47 Then one said unto him, Behold, thy mother and thy brethren stand without, desiring to speak with thee. 48 But he answered and said unto him that told him, Who is my mother? and who are my brethren? 49 And he stretched forth his hand toward his disciples, and said, Behold my mother and my brethren! 50 For whosoever shall do the will of my Father which is in heaven, the same is my brother, and sister, and mother.
The will of God is to believe in the One whom God has sent, Christ. (Jn 6:29, 1 Jn 3:23, Jn 3:16)
Jn 6:29 Jesus answered and said unto them, This is the work of God, that ye believe on him whom he hath sent.
1 Jn 3:23 And this is his commandment, That we should believe on the name of his Son Jesus Christ, and love one another, as he gave us commandment.
Jn 3:16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
If we believe in Jesus as the Christ, we become children of God. And Jesus is our eldest brother. (1 Jn 5:1, Rom 8:29)
1 Jn 5:1 Whosoever believeth that Jesus is the Christ is born of God: and every one that loveth him that begat loveth him also that is begotten of him.
Rom 8:29 For whom he did foreknow, he also did predestinate to be conformed to the image of his Son, that he might be the firstborn among many brethren.