I’m fairly certain that he himself is delusional.
Documents and newspaper announcements and birth certificates can be forged, but the flesh and blood people in these photographs are real. It's not the photographs that are suspect, it's the story the photographs are being USED FOR that is the LIE.
Mark made a huge mistake posting the images of the two little boys on his webpage. He used the image in his dedication of his book to the mythical 'David' - his REAL brother is actually BHO2 - the little boy on the right.