[ebb tide]

[14] All these were persevering with one mind in prayer with the women, and Mary the mother of Jesus, and with his brethren. [15] In those days Peter rising up in the midst of the brethren, said: (now the number of persons together was about an hundred and twenty:) Acts 1

The above is the full quote from Douay-Rheims. Was Peter Christ's sibling? Or are you cherry-picking again?

[ealgeone]

Read the passage on context along with the other already noted passages regarding Joseph and Mary's family.

Remember, Luke is a doctor. He knows the difference between the brothers of Christ and the believers who are referred to as brethren in various places.