After this he went down to Capernaum with his mother and brothers and his disciples. There they stayed for a few days.
“his . . . brothers” = “his brethern” (KJV) were the children of Mary and Joseph, which is called the Helvidian view. Catholics hold that the brethern were either the children of Joseph by a former marriage (the view of Epiphanius) or the cousins of Jesus (the view of Jerome). These various views are necessitated by the idea of Mary’s perpetual virginity. However, Joseph is said to have not known her until after she bore Jesus and in this and another scripture Jesus is called Mary’s “firstborn.” Matt 1:25; Luke 2:7
Matt 1:25 But he had no union with her until she gave birth to a son. And he gave him the name Jesus.
Luke 2:7 and she gave birth to her firstborn, a son. She wrapped him in cloths and placed him in a manger, because there was no room for them in the inn.