Jesus didn't have a biological brother. Mary was a virgin, even up to the time she entered Heaven, body and soul. Jesus was conceived by the Holy Spirit, so Mary was a virgin when she had Jesus. She could not have borne more children because there have been no records of her immaculately conceiving and of having borne more children. (If she bore more children that were not conceived through the Holy Spirit, then she wasn't be a virign, thus, the dogma of her Conception would not exist.). . Jesus was the only one that God made through the Holy Spirit (which is also God, as part of the Holy Trinity), thus people say that God gave the world Jesus, His only son.. But since God is our Father, then we are all brothers and sisters of Jesus, and in Jesus, because he restored to us the experience of God as Father.. . (sorry if you find my explanation confusing. it's the best i can do at 3 a.m. :)