46 While He was still talking to the multitudes, behold, His mother and brothers stood outside, seeking to speak with Him. 47 Then one said to Him, “Look, Your mother and Your brothers are standing outside, seeking to speak with You.”
48 But He answered and said to the one who told Him, “Who is My mother and who are My brothers?” 49 And He stretched out His hand toward His disciples and said, “Here are My mother and My brothers! 50 For whoever does the will of My Father in heaven is My brother and sister and mother.” — Matthew 12:46-50.
Jesus is not showing disrespect for his mother but is going to teach a lesson on who his true spiritual brethren are-they that do his will. We know that Jesus loved and respected his mother (cf. Luke 2:51; John 19:25-27).
In this passage we see Jesus moving from the physical to the spiritual plane. He is teaching that the spiritual relationship that we have with the Lord and with fellow brethren supersedes the relationship that we have with our biological families (cf. John 1:12,13; 2 Corinthians 6:18; Hebrews 2:11).
The only way for us to claim spiritual kinship with the Lord is to do his will and involves out obedience (cf. Matthew 7:21; John 14:15).
Here we find our Lord expanding the definition of His family. He considers all who become His disciples also become His cherished family members. He is defining family by the covenant bond of obedience to God the Father.