Nor do I claim to be....
a theologian. However, were they (Mary & Joseph) married ? Well , perhaps the most quoted passage (Luke 2: 1-20) refers to Mary as Joseph's "betrothed".
What I may (or may not) "believe" (& I have previously "confessed" my belief) doesn't "make the child"...anything. "Bastard" is a defined term. According to Luke, Joseph & Mary were engaged - not married - at time of Jesus birth. According to all of the scriptures God (NOT Joseph) was the father of "the child".
Factually ? Just how do you define "bastard" ? L.
Related link: http://www.biblegateway.com/passage/?search=Luke+2%3A1-20&version=ESV