Ravenwolf, I will put it to you straightforwardly. Adelphos, was a very common, much-used word.
Genesis13
8 And Abram said unto Lot, Let there be no strife, I pray thee, between me and thee, and between my herdmen and thy herdmen; for we be brethren.
They were not brothers but Lot was a nephew.
Also Mary the wife of Cleophas
Matthew 27:56
56 among whom were Mary Magdalene and Mary the mother of James and Joseph and the mother of the sons of Zebedee.
It never mentions Virgin Mary being the mother of these two
but it does mention Mary the wife of Cleophas being their mother.
af_vet_1981 I believe we are getting too tied up with definitions.