Most likely, the people simply wish to draw attention to the fact that Jesus is a local boy. They know his family well and they know that his family does not consist of intellectuals, but of manual labourers. It is interesting to note that at this point in time, Jesus' family did not believe in him. John 7:5 mentions that “even his own brothers did not believe in him.” Later, however, it seems that at the very least, his mother and brothers came to true faith (Acts 1:14; 1 Corinthians 9:5). Some argue that the New Testament letter of James was written by the James mentioned in this verse, and the letter of Jude written by Judas.
3 Is not this the carpenter, the son of Mary and brother of James and Joses and Judas and Simon? And are not his sisters here with us?” And they took offense at him.