Of course. Primary usage of "adelphos" is "brother (of the same parents)". The point is that when a mixture of relatives is described, or when precision is not required, or when a special kinship is indicated, the same word is used. IN SHORT, the Protestant position MUST be admitted to be entirely tenable
The protestant position is indeed tenable from scripture. But so is the Catholic/Orthodox position tenable. You position, however, is not tenable from tradition.
Jesus intentionally distinguishes between these "fellowship brothers" and the "brothers associated with Mary."
He is doing the exact opposite, He intentionally equates the two.
So you're suggesting that someone other than Mary was his mother??