|Lion of St. Mark, Piazza San Marco, Venice|
Members of Jesus' family arrived at his home (3:20), but they couldn't get in because of the large crowds. So they sent in word to Jesus that they were there. Jesus took the opportunity to teach the crowd about the meaning of family.
Did this event take place? There's no way of knowing. The whole passage (3:31-35) is vintage Mark. No details. We don't know what happened afterwards. It's hard to believe that Jesus ignored his mother. What did they talk about? How did Mary express her motherly worries? How did Jesus respond? I think that we can take it, on the basis of Mark 3:20, that Jesus' family was deeply concerned about him and may have shared the fear that he'd become mentally unstable. It seems possible that they'd then taken the trouble to visit him. But we've no way of knowing any of this for certain, and it is just as likely that Mark took some fragment of historical memory and wedded it to Jesus' views on the nature of the family.
The interview the author took his data from might have gone like this: Informant, "Not everybody was so fired up about Jesus. Lots of people thought he was a little strange, maybe even mad. The big shot Pharisees thought he'd been possessed by some kind of an evil spirit." Researcher: "How widespread were these feelings?" Informant: "Pretty widespread I'd say. Even his family worried about him. There was that time when they came to see him." Researcher: "What did they say? What happened?" Informant: "I don't really know. Jesus was teaching a bunch of people, and we were kinda surprised that he didn't just get up and go see his mother. I think they did go off and talk awhile. But, I can't remember exactly. I just remember that they came to see him. They probably wanted him to go back to Nazareth and stop stirring things up so much. The Pharisees were gettin' pretty hot about Jesus by then. You should ask Peter about it. If anybody knows, he does."