James the Persian
Dreptcredincios Crestin
True. That doesn't mean, though, that we do not consider them His siblings - we do. Legally there is no doubt that they were his siblings as legally Joseph was His father. Also, we simply do not know by what means the Incarnation occurred. It is a Mystery that we simply accept did happen. It would not effect Orthodox faith in the slightest if Christ's human nature had been made by God from the human natures of both the Theotokos and Joseph and if hence, the siblings were biologically, if miraculously, real siblings. Of course such would be rank speculation and is utterly irrelevant to the faith, but we do really mean it when we call people like St. James 'Brother of the Lord'.In the West, the siblings of Jesus were generally explained as being his cousins; in the East, they've generally been thought of as the children of Joseph by a previous wife. Neither explanation has any dogmatic significance in any church.
Now on this we must disagree. You appear to be misremembering your Orthodox past, because we simply have no Marian dogmas at all. It is a univerasally held belief within the Church (or so close as to mean that I've never come across anyone that doubts it) that the Theotokos was perpetually virgin, but that does not make it dogma. It isn't. Questioning the belief would not put you outside of the Orthodox faith any more than St. John Chrysostom's opinion that the Theotokos sinned at Canaa put him out of the faith - and the belief in the sinlessness of the Theotokos is every bit as universally held and every bit as frequently expressed in the liturgy etc. as is her perpetual virginity.However, all the historic churches -- the Roman Catholic, Eastern Orthodox, Oriental Orthodox, and Assyrian churches -- affirm the perpetual virginity of the Mother of God, and while I'm not sure about the Assyrian Church of the East, it's a point of dogma for at least the first three. A belief in her perpetual virginity was also held by the great reformers -- Luther, Calvin and Zwingli -- and by John Wesley.
James