Certainly, the expression of 'brothers' of Christ had a cultic meaning, and was the objective of all Christians.
The tradition of Jeus also having literal brothers was arrived at an early stage in the second century proto-orthodoxy as a means to oppose Docetism (the early/original assertion that the Christ was not actually human but had taken the appearance). This development was enabled by the "too-many-Marys" conflation/confusion problems and two brief usages in Pauline material in reference to certain Christian men, perhaps in a special usage reflecting rank.
Mark preserves an older reference to a Mary, who was a disciple in 15:
40 Some women were watching from a distance. Among them were Mary Magdalene, Mary the mother of James the younger and of Joseph,[d] and Salome. 41 In Galilee these women had followed him and cared for his needs. Many other women who had come up with him to Jerusalem were also there.
Contrast that with 6:
3 Isn’t this the carpenter? Isn’t this Mary’s son and the brother of James, Joseph,[a] Judas and Simon? Aren’t his sisters here with us?” And they took offense at him.
The bold lines almost certainly were added, perhaps as a harmonization with the Matthean (13:55) expansion/redaction of this passage.
Anyway, this adjustment to the euhemerization process served a purpose early on but later, once the proto-orthodoxy became thoroughly dominant, it was an embarrassment, requiring another layer of tradition that gave a widowed Joseph children from a previous marriage.