I see that the conversation is shifting a little and I'm coming in late but I wanted to give my opinion on this matter. I'm not sure I believe these children were from a previous marriage. First there is no, at least to my knowledge, mention anywhere in the scripture of Joseph having been married before Mary. So far I have found nothing in the scripture to suggest that the "sons" he had were his biological children at all. The OT and a couple of the writers of the NT give the genealogy up to Joseph but never mentions any of his children in the genealogy. Sometimes the bible gives the impression that it is big on mentioning the first born males of the house. I find that interesting because in the genealogy that is given they go way back but there is no mention of Joseph's first born son in it. To my knowledge they only list Yeshua, who was not even his blood related child. Additionally what I find interesting is that throughout the travel, before Yeshua was born, there is no mention of Joseph's children journeying with them when Mary was pregnant. It doesn't appear that these children, before Yeshua, were Mary's children as suggested in Luke 1:34.
Just my opinion......