[wagglebee]

There is no mention to physical brothers or sisters in Mark 3. There is mention of physical relation to the Blessed Mother, hence the title Mother of God.

I believe the Church is built upon Jesus Christ.

No, Jesus said "on this Rock (Peter) I will build My Church." He did not say to Peter, "build My Church on Me."

[marajade]

Mark 3:31: "There came then his brethren..." So you are saying that the physical brethren in this scripture is physical to Mary, Jesus' mother, but not to him? Am I understanding you correctly?

No, it was Peter's confession that Jesus was the Messiah. That confession that Jesus is the Messiah is the rock upon which Jesus' church was built.