Dates would help to determine some facts. My ancestor, Daniel Iman, came to MO from WV in 1818 and settled in St Charles County MO with his new bride and soon his son, Christopher Washington Iman was born. I do not have any info on David Iman, but there were Imans in PA where they originally settled in Lancaster County. There were several Imans named Christian or Christopher, and at times the names were used interchangably [this is proven by a land transfer paper in Hardy Co, WV]. It is fairly sure that those two you mention are related, and therefore you and I are also.
Raymond Iman
riman@maain.com