[55] Is not this the carpenter's son? Is not his mother called Mary? And are not his brothers James and Joseph and Simon and Judas?
[56] And are not all his sisters with us? Where then did this man get all this?"
Oh Mack you just don't get it. The four brothers/brethren were all the men there. All the sisters weren't identified but we are fortunate that the entire group of men (brothers/brethren) were identified.
Get it now?
By the same token Mark 3:32 And a crowd was sitting about him; and they said to him, "Your mother and your brothers are outside, asking for you." The "crowd" sitting about him didn't include any "brothers", they were all outside with his mother.
Now do you get it?